. 09 / 332, 502, titled, “ system and method for intrusion detection using a time domain radar array, ” and u. s. patent application ser. no. 09 / 332, 503, titled, “ wide area time domain radar array, ” both filed on jun. 14, 1999, and both of which are assigned to the assignee of the present invention. the above patent documents are incorporated herein by reference. this section provides an overview of impulse radio technology and relevant aspects of communications theory. it is provided to assist the reader with understanding the present invention and should not be used to limit the scope of the present invention. it should be understood that the terminology ‘ impulse radio ’ is used primarily for historical convenience and that the terminology can be generally interchanged with the terminology ‘ impulse communications system, ultra - wideband system, or ultra - wideband communication systems ’. furthermore, it should be understood that the described impulse radio technology is generally applicable to various other impulse system applications including but not limited to impulse radar systems and impulse positioning systems. accordingly, the terminology ‘ impulse radio ’ can be generally interchanged with the terminology ‘ impulse transmission system and impulse reception system. ’ impulse radio refers to a radio system based on short, low duty - cycle pulses. an ideal impulse radio waveform is a short gaussian monocycle. as the name suggests, this waveform attempts to approach one cycle of radio frequency ( rf ) energy at a desired center frequency. due to implementation and other spectral limitations, this waveform may be altered significantly in practice for a given application. many waveforms having very broad, or wide, spectral bandwidth approximate a gaussian shape to a useful degree. impulse radio can use many types of modulation, including amplitude modulation, phase modulation, frequency modulation, time - shift modulation ( also referred to as pulse - position modulation or pulse - interval modulation ) and m - ary versions of these. in this document, the time - shift modulation method is often used as an illustrative example. however, someone skilled in the art will recognize that alternative modulation approaches may, in some instances, be used instead of or in combination with the time - shift modulation approach. in impulse radio communications, inter - pulse spacing may be held constant or may be varied on a pulse - by - pulse basis by information, a code, or both. generally, conventional spread spectrum systems employ codes to spread the normally narrow band information signal over a relatively wide band of frequencies. a conventional spread spectrum receiver correlates these


more detail in u. s. pat. no. 5, 677, 927 to fullerton et al. impulse transmission systems are based on short, low duty - cycle pulses. different pulse waveforms, or pulse types, may be employed to accommodate requirements of various applications. typical pulse types include a gaussian pulse, pulse doublet ( also referred to as a gaussian monocycle ), pulse triplet, and pulse quadlet as depicted in figs. 1a through 1d, respectively. an actual received waveform that closely resembles the theoretical pulse quadlet is shown in fig. 1e. a pulse type may also be a wavelet set produced by combining two or more pulse waveforms ( e. g., a doublet / triplet wavelet set ). these different pulse types may be produced by methods described in the patent documents referenced above or by other methods, as persons skilled in the art would understand. for analysis purposes, it is convenient to model pulse waveforms in an ideal manner. for example, the transmitted waveform produced by supplying a step function into an ultra - wideband antenna may be modeled as a gaussian monocycle. a gaussian monocycle ( normalized to a peak value of 1 ) may be described by where σ is a time scaling parameter, t is time, and e is the natural logarithm base. the power spectral density of the gaussian monocycle is shown in fig. 1f, along with spectrums for the gaussian pulse, triplet, and quadlet. the corresponding equation for the gaussian monocycle is : the center frequency ( fc ), or frequency of peak spectral density, of the gaussian monocycle is : it should be noted that the output of an ultra - wideband antenna is essentially equal to the derivative of its input. accordingly, since the pulse doublet, pulse triplet, and pulse quadlet are the first, second, and third derivatives of the gaussian pulse, in an ideal model, an antenna receiving a gaussian pulse will transmit a gaussian monocycle and an antenna receiving a gaussian monocycle will provide a pulse triplet. pulse trains impulse transmission systems may communicate one or more data bits with a single pulse ; however, typically each data bit is communicated using a sequence of pulses, known as a pulse train. as described in detail in the following example system, the impulse radio transmitter produces and outputs a train of pulses for each bit of information.


application titled “ a method for specifying non - allowable pulse characteristics, ” application ser. no. 09 / 592, 289, filed jun. 12, 2000, and incorporated herein by reference. a related method that conditionally positions pulses depending on whether code elements map to non - allowable regions is described in co - owned, co - pending application, titled “ a method and apparatus for positioning pulses using a layout having non - allowable regions, ” application ser. no. 09 / 592, 248 filed jun. 12, 2000, and incorporated herein by reference. the signal of a coded pulse train can be generally expressed by : where k is the index of a transmitter, j is the index of a pulse within its pulse train, ( −1 ) fj ( k ), aj ( k ), bj ( k ), cj ( k ), and ω ( t, bj ( k ) ) are the coded polarity, pulse amplitude, pulse type, pulse width, and normalized pulse waveform of the jth pulse of the kth transmitter, and tj ( k ) is the coded time shift of the jth pulse of the kth transmitter. note : when a given non - temporal characteristic does not vary ( i. e., remains constant for all pulses ), it becomes a constant in front of the summation sign. various numerical code generation methods can be employed to produce codes having certain correlation and spectral properties. such codes typically fall into one of two categories : designed codes and pseudorandom codes. a designed code may be generated using a quadratic congruential, hyperbolic congruential, linear congruential, costas array, or other such numerical code generation technique designed to generate codes having certain correlation properties. a pseudorandom code may be generated using a computer ' s random number generator, binary shift - register ( s ) mapped to binary words, a chaotic code generation scheme, or the like. such ‘ random - like ’ codes are attractive for certain applications since they tend to spread spectral energy over multiple frequencies while having ‘ good enough ’ correlation properties, whereas designed codes may have superior correlation properties but possess less suitable spectral properties. detailed descriptions of numerical code generation techniques are included in a co - owned, co - pending patent application titled “ a method and apparatus for positioning pulses in time, ” application ser. no. 09 / 592, 248, filed jun. 12, 2000, and incorporated herein by reference. it may be necessary to


, co - pending patent application titled “ a method and apparatus for positioning pulses in time, ” application ser. no. 09 / 592, 248, filed jun. 12, 2000, and incorporated herein by reference. it may be necessary to apply predefined criteria to determine whether a generated code, code family, or a subset of a code is acceptable for use with a given uwb application. criteria may include correlation properties, spectral properties, code length, non - allowable regions, number of code family members, or other pulse characteristics. a method for applying predefined criteria to codes is described in co - owned, co - pending application, titled “ a method and apparatus for specifying pulse characteristics using a code that satisfies predefined criteria, ” application ser. no. 09 / 592, 288, filed jun. 12, 2000, and incorporated herein by reference. in some applications, it may be desirable to employ a combination of codes. codes may be combined sequentially, nested, or sequentially nested, and code combinations may be repeated. sequential code combinations typically involve switching from one code to the next after the occurrence of some event and may also be used to support multicast communications. nested code combinations may be employed to produce pulse trains having desirable correlation and spectral properties. for example, a designed code may be used to specify value range components within a layout and a nested pseudorandom code may be used to randomly position pulses within the value range components. with this approach, correlation properties of the designed code are maintained since the pulse positions specified by the nested code reside within the value range components specified by the designed code, while the random positioning of the pulses within the components results in particular spectral properties. a method for applying code combinations is described in co - owned, co - pending application, titled “ a method and apparatus for applying codes having pre - defined properties, ” application ser. no. 09 / 591, 690, filed jun. 12, 2000, and incorporated herein by reference. various aspects of a pulse waveform may be modulated to convey information and to further minimize structure in the resulting spectrum. amplitude modulation, phase modulation, frequency modulation, time - shift modulation and m - ary versions of these were proposed in u. s. pat. no. 5, 677, 927 to fullerton et al., previously incorporated by reference. time - shift modulation can be described as shifting the position of a pulse either forward or


versions of these were proposed in u. s. pat. no. 5, 677, 927 to fullerton et al., previously incorporated by reference. time - shift modulation can be described as shifting the position of a pulse either forward or backward in time relative to a nominal coded ( or uncoded ) time position in response to an information signal. thus, each pulse in a train of pulses is typically delayed a different amount from its respective time base clock position by an individual code delay amount plus a modulation time shift. this modulation time shift is normally very small relative to the code shift. in a 10 mpps system with a center frequency of 2 ghz, for example, the code may command pulse position variations over a range of 100 ns, whereas, the information modulation may shift the pulse position by 150 ps. this two - state ‘ early - late ’ form of time shift modulation is depicted in fig. 4a. a pulse train with conventional ‘ early - late ’ time - shift modulation can be expressed : where k is the index of a transmitter, j is the index of a pulse within its pulse train, ( −1 ) fj ( k ), aj ( k ), bj ( k ), cj ( k ), and ω ( t, bj ( k ) ) are the coded polarity, pulse amplitude, pulse type, pulse width, and normalized pulse waveform of the jth pulse of the kth transmitter, tj ( k ) is the coded time shift of the jth pulse of the kth transmitter, δ is the time shift added when the transmitted symbol is 1 ( instead of 0 ), d ( k ) is the data ( i. e., 0 or 1 ) transmitted by the kth transmitter, and ns is the number of pulses per symbol ( e. g., bit ). similar expressions can be derived to accommodate other proposed forms of modulation. an alternative form of time - shift modulation can be described as one - of - many position modulation ( ompm ). the ompm approach, shown in fig. 4b, involves shifting a pulse to one of n possible modulation positions about a nominal coded ( or uncoded ) time position in response to an information signal, where n represents the number of possible states. for example, if n were four ( 4 ), two data bits of information could be conveyed. for further details regarding ompm, see “ apparatus, system and method for one - of - many position modulation in an impulse radio communication


possible states. for example, if n were four ( 4 ), two data bits of information could be conveyed. for further details regarding ompm, see “ apparatus, system and method for one - of - many position modulation in an impulse radio communication system, ” attorney docket no. 1659. 0860000, filed jun. 7, 2000, assigned to the assignee of the present invention, and incorporated herein by reference. an impulse radio communications system can employ flip modulation techniques to convey information. the simplest flip modulation technique involves transmission of a pulse or an inverted ( or flipped ) pulse to represent a data bit of information, as depicted in fig. 4c. flip modulation techniques may also be combined with time - shift modulation techniques to create two, four, or more different data states. one such flip with shift modulation technique is referred to as quadrature flip time modulation ( qftm ). the qftm approach is illustrated in fig. 4d. flip modulation techniques are further described in patent application titled “ apparatus, system and method for flip modulation in an impulse radio communication system, ” application ser. no. 09 / 537, 692, filed mar. 29, 2000, assigned to the assignee of the present invention, and incorporated herein by reference. vector modulation techniques may also be used to convey information. vector modulation includes the steps of generating and transmitting a series of time - modulated pulses, each pulse delayed by one of at least four pre - determined time delay periods and representative of at least two data bits of information, and receiving and demodulating the series of time - modulated pulses to estimate the data bits associated with each pulse. vector modulation is shown in fig. 4e. vector modulation techniques are further described in patent application titled “ vector modulation system and method for wideband impulse radio communications, ” application ser. no. 09 / 169, 765, filed dec. 9, 1999, assigned to the assignee of the present invention, and incorporated herein by reference. reception and demodulation impulse radio systems operating within close proximity to each other may cause mutual interference. while coding minimizes mutual interference, the probability of pulse collisions increases as the number of coexisting impulse radio systems rises. additionally, various other signals may be present that cause interference. impulse radios can operate in the presence of mutual interference and other interfering signals, in part because they do not depend on receiving every transmitted pulse. impulse radio receivers perform a correlating, synchronous receiving function


functions of the transmitter 602 and receiver 702. some of these include the time base 718, precision timing generator 714, code source 722, antenna 704, and the like. figs. 8a - 8c illustrate the cross correlation process and the correlation function. fig. 8a shows the waveform of a template signal. fig. 8b shows the waveform of a received impulse radio signal at a set of several possible time offsets. fig. 8c represents the output of the cross correlator for each of the time offsets of fig. 8b. for any given pulse received, there is a corresponding point that is applicable on this graph. this is the point corresponding to the time offset of the template signal used to receive that pulse. further examples and details of precision timing can be found described in u. s. pat. no. 5, 677, 927, and commonly owned co - pending application application ser. no. 09 / 146, 524, filed sep. 3, 1998, titled “ precision timing generator system and method, ” both of which are incorporated herein by reference. because of the unique nature of impulse radio receivers, several modifications have been recently made to enhance system capabilities. modifications include the utilization of multiple correlators to measure the impulse response of a channel to the maximum communications range of the system and to capture information on data symbol statistics. further, multiple correlators enable rake pulse correlation techniques, more efficient acquisition and tracking implementations, various modulation schemes, and collection of time - calibrated pictures of received waveforms. for greater elaboration of multiple correlator techniques, see patent application titled “ system and method of using multiple correlator receivers in an impulse radio system ”, application ser. no. 09 / 537, 264, filed mar. 29, 2000, assigned to the assignee of the present invention, and incorporated herein by reference. methods to improve the speed at which a receiver can acquire and lock onto an incoming impulse radio signal have been developed. in one approach, a receiver includes an adjustable time base to output a sliding periodic timing signal having an adjustable repetition rate and a decode timing modulator to output a decode signal in response to the periodic timing signal. the impulse radio signal is cross - correlated with the decode signal to output a baseband signal. the receiver integrates t samples of the baseband signal and a threshold detector uses the integration results to detect channel coincidence. a receiver


pp. 73 - 79 ). these three acquaintances parallel the requirements for a proposition ’ s being true ( on a correspondence theory of truth ) : ( a ) the truth - maker ( s is directly acquainted with the fact that p ) ; ( b ) the truth - bearer ( s is directly acquainted with the thought that p ) ; and ( c ) the correspondence relation ( s is directly acquainted with the correspondence between the fact that p and the thought that p ). given the subject ’ s direct acquaintance with ( i ), ( ii ), and ( iii ), he is directly acquainted with everything necessary to constitute being directly acquainted with a true proposition. to the extent that bonjour provides an account of knowledge by acquaintance, it is directed exclusively to basic empirical beliefs. bonjour describes his theory of basic empirical justification as taking place when a person directly apprehends that his experience fits or satisfies the description offered by the content of his belief ( bonjour 2001 ; bonjour 2003, especially pp. 60 - 76, 191 - 193 ; bonjour uses the language of “ direct acquaintance ” in 2001, while he prefers “ direct apprehension ” in 2003 ). it is the subject ’ s ability to have a direct acquaintance or apprehension of the contents of one ’ s own conscious experiences and how they fit or satisfy the content of one ’ s basic beliefs that makes knowledge by acquaintance possible. bonjour stresses, however, that fallibility can occur due to the subject ’ s misapprehension of one ’ s experience or failure to see the fit between the experience and the belief. despite the possibility of error, he believes that this does not undermine genuine cases when a subject does correctly apprehend the character of experience and sees its fit with one ’ s basic belief. on the other hand, there are non - traditional acquaintance theorists who have modified knowledge by acquaintance in such a way that one can be acquainted with and know physical objects directly ( such as brewer 2011 ). another deviation from the russellian tradition is to maintain that knowledge by acquaintance is a different kind of knowledge than propositional knowledge ( tye 2009, pp. 95 - 102 ). on this non - propositional approach to knowledge by acquaintance, there is a sense in which one can be said to know something with which one is acquainted, even though the person does not necessarily have any propositional belief states about the thing that is said to be known by acquaintance. perhaps the most influential problem raised for knowledge by acquaintance is commonly called the problem


said to know something with which one is acquainted, even though the person does not necessarily have any propositional belief states about the thing that is said to be known by acquaintance. perhaps the most influential problem raised for knowledge by acquaintance is commonly called the problem of the speckled hen ( due to gilbert ryle as reported by chisholm 1942 ). the problem arises by considering the case where someone looks at a hen with exactly 48 speckles on one side. yet, the perceiver ’ s experience is not adequate grounds for him to distinguish an experience of a hen with exactly 47 or 49 speckles. indeed, even if someone were to hold the belief that one ’ s experience is of a hen with exactly 48 speckles, it would by most standards fail to count as knowledge because the subject could have easily formed a false belief ( for example, that the hen has 47 or 49 speckles ) on the basis of being acquainted with that very experience ( for one way to understand this epistemic principle see “ the safety condition for knowledge ” ). in other words, typically people cannot distinguish between having a visual experience of a 47, 48, or 49 speckled hen. however, if a person is directly acquainted with these experiences and can plausibly satisfy the other conditions required for knowledge by acquaintance, then cases of this sort stand as potential counterexamples to possessing knowledge or justification through direct acquaintance. given the indiscernibility of the contents of mental states through direct acquaintance, this raises doubts whether one ’ s justification based on direct acquaintance can offer some unique, privileged state of knowledge. after all, one motivation for accepting knowledge by acquaintance is that the subject ’ s knowledge of his own mental states may be indubitable, whereas other kinds of knowledge cannot. the problem of the speckled hen challenges the idea that one may fail to have indubitable justification through knowledge by acquaintance because for just about any putative mental state with which one is acquainted, since there may be a different mental state that is virtually indistinguishable from it. it even raises the question whether these closely related states constitute genuinely different experiences for the subject at all. the problem of the speckled hen has continued to challenge contemporary accounts of knowledge by acquaintance ( see sosa 2003a, 2003b ; markie 2009 ; poston 2010 ). the challenge, as sosa puts it, is for the acquaintance theorist to “ tell us which sorts of features of our states of consciousness are epistemically effective ones


belief - states involving phenomenal concepts can accommodate the challenge of the speckled hen by plausibly maintaining that the concept of being 48 - speckled is not a phenomenal concept and thereby not a candidate for knowledge by acquaintance. third, one can maintain that there are degrees between determinate and determinable properties with which one is acquainted ( compare fales 1996, pp. 173 - 180 ). properties fall on a continuum between being more general to being more specific or determined. for example, a ripe tomato ’ s surface can be described generally as colored, more determinately as red, or even more determinately as vermilion. given this distinction in the determinateness of properties, it is possible that one could be directly acquainted with differing degrees of determinable properties. if experiences can instantiate varying degrees of these determinable properties ( and this is a matter of controversy that cannot be addressed here ), then in cases like the speckled hen the acquaintance theorist may hold that the subject is not directly acquainted with the experience of a hen with 48 speckles but with the experience having a less determinate property such as the property of being many - speckled. thus, in cases akin to the speckled hen, the subject may not be acquainted with the property of being 48 - speckled, but with a less determinate property like being many - speckled. another proposed solution to the problem of the speckled hen follows from distinguishing between the phenomenal and epistemic appearances of an experience ( gertler 2011, pp. 103 - 106 ). the phenomenal appearance of an experience is determined by the properties that constitute the experience. the epistemic appearance of an experience is what the experience inclines the subject to believe. for example, if someone takes a white plate and holds it under a green light, the plate phenomenally appears green ( that is, the property of being green partly constitutes the experience of the plate ) but with sufficient knowledge of the effects of green lighting on white objects, it does not epistemically appear green ( that is, the subject is not inclined to think that the plate is green ). in cases like the speckled hen, then, the experience may phenomenally appear to be 48 - speckled, but it may only epistemically appear to be many - speckled. the key to this solution is disambiguating the meaning of “ appearance ” to explain how in one sense the subject may have an appearance of a hen with 48 speckle


may only epistemically appear to be many - speckled. the key to this solution is disambiguating the meaning of “ appearance ” to explain how in one sense the subject may have an appearance of a hen with 48 speckles ( phenomenally ) and in another sense the subject may not have an appearance of a hen with 48 speckles ( epistemically ). with respect to the sellarsian dilemma, one response takes the horn of the dilemma that states propositional beliefs derive their justification from non - propositional experiences. for instance, fumerton ( 1995, pp. 74 - 76 ) proposes an account of knowledge by acquaintance ( see above section 2b ) where the subject is in a position to know a truth through three acquaintances. since acquaintance by itself is not an epistemic concept in need of justification, it enables the subject to be appropriately related to the source of one ’ s justification without necessitating further levels of justification. thus, in response to the challenge to explain how non - propositional experiences ( such as the raw experience of searing pain ) can justify propositional thoughts ( such as the belief that i am experiencing pain ), fumerton maintains that justification is made possible by being directly acquainted with the relation of correspondence that holds between the non - propositional experience and the propositional thought. bonjour offers another influential response to sellars ’ s dilemma ( 2001, pp. 28 - 34 ; 2003, especially pp. 69 - 74 ). on bonjour ’ s account of basic empirical knowledge ( see above section 2b ), the awareness or apprehension of the justification for one ’ s belief is built - in or partly constitutive of the justifying non - conceptual experience. while non - conceptual experiences do not stand in certain kinds of logical relations ( for example, inferring ) to conceptual beliefs, there is a relation of description or fit that holds between experiences and beliefs. since certain kinds of experiences have a built - in awareness of their contents, these experiences contain within themselves a kind of reason for thinking that the given description accurately fits. the crucial move in bonjour ’ s solution is to see that the built - in awareness renders the basic empirical belief justified without any further need for justification. staunch defenders of the sellarsian dilemma will likely remain unimpressed with these responses. the problem, they might urge, is that these alleged solutions push the problem back a level. those defending the dilemma will press these proposals to explain how propositional


staunch defenders of the sellarsian dilemma will likely remain unimpressed with these responses. the problem, they might urge, is that these alleged solutions push the problem back a level. those defending the dilemma will press these proposals to explain how propositional beliefs can correspond or accurately describe non - propositional experiences. in some places, fumerton and bonjour seem to suggest that first - hand experience with our own conscious states of mind adequately demonstrate how these relations are able to hold ( fumerton 1995, p. 77 ; bonjour 2003, pp. 69 - 74 ). other friends of direct acquaintance have suggested that experiences, while being non - propositional, may have a propositional structure ( or proto - propositional structure ) that allows for propositional content to map onto it ( fales 1996, pp. 166 - 169 ). for example, a non - propositional experience may be constituted by presenting particulars exemplifying specific properties, which naturally provides a structure resembling statements in the subject - predicate form. timothy mcgrew contends that basic empirical beliefs can be formed by indexically referring to one ’ s non - propositional experience as part of what constitutes the propositional content of the belief ( 1995, especially pp. 89 - 90 ). by embedding the non - propositional content as a constituent part of the belief ( for example, “ i am being appeared to thusly ” ), it is possible to show how non - propositional experiences may provide a basis for forming justified propositional beliefs ( for some concerns about the richness of indexically formed beliefs to serve as a foundation see sosa 2003b, especially pp. 122 - 124 ). while knowledge by acquaintance has its most immediate application to philosophical topics in epistemology, it has increasingly been applied to issues in metaphysics, especially in the philosophy of mind. in particular, knowledge by acquaintance has played a role in the knowledge argument against physicalism. some argue that knowledge of qualia is direct and unmediated, which provides an insight into the nature of the mind that cannot be known through the physical sciences. frank jackson presents this argument through a compelling thought experiment about mary ( jackson 1982 ; 1986 ). mary is a scientist who learns all the physical truths from her exhaustive study of the completed physics. for whatever reasons, mary has lived her entire life without experiencing any colors besides black, white, and shades of gray. one day after she has mastered all the physical truths and everything that can be deduced a prior


by suggesting that one can know all the propositional truths about something ( for example, the city of houston ) and yet not know it directly. the difference between knowledge of phenomenal consciousness and knowledge of brain states is like the difference between knowing about houston ( by reading a very thorough visitor ’ s guide ) and knowing houston directly ( by visiting the city ). according to these views, it is because knowledge by acquaintance is a different kind of knowledge that phenomenal knowledge appears to differ from descriptive, physical knowledge about brain states. although there is not space for a full evaluation of these views, one problem that has been raised is that knowledge by acquaintance cannot by itself account for the epistemic disparity that this solution is attempting to solve ( see nida - rumelin 1995 ; gertler 1999 ). in other words, the problem is that there appears to be propositional, factual content about the properties of conscious experience that these non - standard accounts of knowledge by acquaintance fail to capture. the distinction between knowledge by acquaintance and knowledge by description has a number of important applications in philosophy. in epistemology, it underwrites a tradition from bertrand russell that continues to influence debates on the nature of foundationalism and the possibility of a privileged class of knowledge. in metaphysics, knowledge by acquaintance has increasingly been incorporated into arguments concerning the nature of conscious experience and the viability of physicalism. the current trend suggests that knowledge by acquaintance will continue to be refined and put to work on a variety of philosophical fronts. - balog, k. 2012. “ acquaintance and the mind - body problem. ” in simone gozzano and christopher hill ( eds. ), new perspectives on type identity : the mental and the physical ( pp. 16 - 43 ). cambridge : cambridge university press. - bonjour, l. 2001. “ toward a defense of empirical foundationalism. ” in michael raymond depaul ( ed. ), resurrecting old - fashioned foundationalism ( pp. 21 - 38 ). lanham : rowman and littlefield. - bonjour, l. 2003. “ a version of internalist foundationalism. ” in laurence bonjour and ernest sosa ( eds. ), epistemic justification : internalism vs. externalism, foundations vs. virtues ( pp. 5 - 96 ). malden : blackwell. - brewer, b. 2011. perception and its objects. oxford : oxford university press. - chalmers, d. 1996. the conscious mind.


. externalism, foundations vs. virtues ( pp. 5 - 96 ). malden : blackwell. - brewer, b. 2011. perception and its objects. oxford : oxford university press. - chalmers, d. 1996. the conscious mind. oxford : oxford university press. - chalmers, d. 2003. “ the content and epistemology of phenomenal belief. ” in quentin smith and aleksandar jokic ( eds. ), consciousness : new philosophical perspectives ( pp. 220 - 272 ). oxford : oxford university press. - chalmers, d. 2004. “ phenomenal concepts and the knowledge argument. ” in peter ludlow, yujin nagasawa, and daniel stoljar ( eds. ), there ’ s something about mary : essays on phenomenal consciousness and frank jackson ’ s knowledge argument ( pp. 269 - 298 ). cambridge : mit press. - chalmers, d. 2007. “ phenomenal concepts and the explanatory gap. ” in torin alter and sven walter ( eds. ), phenomenal concepts and phenomenal knowledge : new essays on consciousness and physicalism ( pp. 167 - 194 ). oxford : oxford university press. - chisholm, r. 1942. “ the problem of the speckled hen. ” mind 51, 368 - 373. - conee, e. 1994. “ phenomenal knowledge. ” australasian journal of philosophy 72, 136 - 150. - davidson, d. 1986. “ a coherence theory of truth and knowledge. ” in ernest lepore ( ed. ), truth and interpretation : perspectives on the philosophy of donald davidson ( pp. 423 - 438 ). malden : blackwell. - fales, e. 1996. a defense of the given. lanham : rowman and littlefield. - feldman, r. 2004. “ the justification of introspective beliefs. ” in earl conee and richard feldman ( eds. ), evidentialism : essays in epistemology ( pp. 199 - 218 ). oxford : oxford university press. - fumerton, r. 1995. metaepistemology and skepticism. lanham : rowman and littlefield. - fumerton, r. 2005. “ speckled hens and objections of acquaintance. ” philosophical perspectives 19, 121 - 138. - gertler, b. 1999. “ a defense of the knowledge argument. ” philosophical studies 93, 317 - 336. - gertler, b. 2001


hens and objections of acquaintance. ” philosophical perspectives 19, 121 - 138. - gertler, b. 1999. “ a defense of the knowledge argument. ” philosophical studies 93, 317 - 336. - gertler, b. 2001. “ introspecting phenomenal states. ” philosophy and phenomenological research 63, 305 – 328. - gertler, b. 2011. self - knowledge. new york : routledge. - gertler, b. 2012. “ renewed acquaintance. ” in declan smithies and daniel stoljar ( eds. ), introspection and consciousness ( pp. 93 - 128 ). oxford : oxford university press. - hasan, a. forthcoming. “ phenomenal conservatism, classical foundationalism, and internalist justification. ” philosophical studies. - jackson, f. 1982. “ epiphenomenal qualia. ” philosophical quarterly 32, 126 - 136. - jackson, f. 1986. “ what mary didn ’ t know. ” the journal of philosophy 83, 291 - 295. - markie, p. 2009. “ classical foundationalism and speckled hens. ” philosophy and phenomenological research 79, 190 - 206. - mcgrew, t. 1995. the foundations of knowledge. lanham : littlefield adams. - nida - rumelin, m. 1995. “ what mary couldn ’ t know : belief about phenomenal states. ” in thomas metzinger ( ed. ), conscious experience ( pp. 219 - 241 ). exeter : imprint academic. - pitt, d. “ the phenomenology of cognition, or, what it is like to think that p? ” philosophy and phenomenological research 69, 1 - 36. - poston, t. 2007. “ acquaintance and the problem of the speckled hen. ” philosophical studies 132, 331 - 346. - poston, t. 2010. “ similarity and acquaintance. ” philosophical studies 147, 369 - 378. - russell, b. 1905. “ on denoting. ” mind 14, 479 - 493. - russell, b. 1910. “ knowledge by acquaintance and knowledge by description. ” proceedings of the aristotelian society 11, 108 - 128. - russell, b. 1997. problems of philosophy, ed. john perry. oxford : oxford university press. - russell, b. 1993. our knowledge of the external world. new york : routledge. - sellars


2006 08 11 by ker than | usatoday. com a two - year survey of enormous interstellar dust clouds has turned up eight organic molecules in two different regions of space. one is a stellar nursery awash in light while the other is a cold, starless void. the finding, detailed in the current issue of astrophysical journal, supports other recent studies suggesting molecules important for life commonly form in the gas and dust clouds that condense to form stars and planets. the molecules were discovered using the robert c. byrd green bank telescope ( gbt ), a large radio telescope located in west virginia. " finding eight [ organic ] molecules in the space of two years is quite remarkable, " said study leader jan hollis of nasa goddard space flight center. the newly discovered molecules are made up of 6 to 11 atoms each and are classified as organic because they contain carbon. five of the molecules were discovered in sagittarius b2 ( n ), a star - forming dust cloud located 26, 000 light - years from earth near the center of the milky way galaxy. this stellar nursery is the largest known repository of complex interstellar molecules. the other three molecules were found in the taurus molecular cloud ( tmc - 1 ), located only 450 light - years away. tmc - 1 is starless ; it is cold and dark and has a temperature of only 10 degrees above absolute zero. " the discovery of these large organic molecules in the coldest regions of the interstellar medium has certainly changed the belief that large organic molecules would only have their origins in hot molecular cores, " said study team member anthony remijan of the national radio astronomy observatory ( nrao ). " it has forced us to rethink the paradigms of interstellar chemistry. " just because a molecule is organic does not mean that it is made by living things. in fact, many of the newly spotted molecules are poisonous to organisms on earth, hollis said. but one of the molecules found in sagittarius b2 ( n ), called acetamide, contains a type of chemical bond important for linking together amino acids, the molecular building blocks of proteins. made up of 9 atoms, acetamide " is the largest molecule found in space that has that bond, " hollis told space. com. the molecules are thought to form by two main mechanisms. in the first, simple chemical reactions add an atom to a molecule that is stuck to the surface of a dust grain afloat in space. the second method involves chemical reactions between neutral


laser technology uses light. light can be rapidly and precisely deflected, shaped and focused. if we pulse laser light and reduce pulse duration more and more, the laser tool works even more precisely. a benefit : the material being processed heats up less and less. high - power, ultra - short pulses, then, are the ideal solution for medical applications, in brain surgery for instance, as the cerebral membrane is not damaged. or for removing tumor tissue thereby conserving the surrounding tissue and blood vessels. this precision technology is also valued in the processing of materials, glass for instance : lasers are able to cut narrow speaker ports in smartphone displays. for years, ultra - short laser pulses have been used for the extremely precise and gentle processing of highly - sensitive materials. until now though, they have often lacked in power. the newly developed laser platform solves this problem with the innoslab amplifier as its core. four mirrors surround a laser crystal plate – the slab. pump radiation enters at the two opposite faces of the slab. ultra - short laser pulses are repeatedly reflected by these mirrors and pass through the slab several times. energy is transfered from the pump radiation to the laser pulse until the required power is achieved. the innoslab platform was developed by the fraunhofer institute for laser technology ilt in aachen and refined further together with several partners from industry and science : the chair for laser technology at rwth aachen university, the max planck institute for quantum optics mpq in munich and the companies jenoptik ag, edgewave and amphos – the latter two being ilt spin - offs. to develop new markets for laser systems with ultra - short wavelengths, the team of developers had to increase the mean laser output of ultra - short pulse beam sources – up to several hundred watts. higher power makes high volume production in industrie and shorter measuring times during scientific experiments possible. between 2008 and 2011, two joint projects revolved around developing the new beam source : the aim of the pikoflat project, supported by the federal ministry for education and research bmbf, was to structure printing tools and embossing dies. the goal was to reduce processing times while significantly increasing quality. one of the results of this project is the production of embossing cylinders that are used to create extremely fine artificial leather surfaces for the automotive industry. in the second joint project, korona, fraunhofer collaborated closely with the max planck institute of quantum optics in garching near munich and with rwth aachen university


a drug is a chemical or biochemical compose able to deteriorate one or more intraneuronales activities and / or to disturb the communications interneuronales. the man recognized the capacity of drugs very early in his history and consumed those since then in order to modifying his physiological or psychic functions, his physiological reactions and his state of consciousnesses. and which can be mortal ( the ground is punt man! *! e! exchange. ) certain drugs can generate a dependence physical or psychological. the use of those can have as consequences of the physical or mental disturbances. the term “ drug ” recovers primarily two aspects : the nature of the biological effects that drug induced on the one hand, and on the other hand reports / ratios that which consumes it maintains with it. it is necessary that a given chemical compound either consumed so that it can answer the name of “ drug ”. it is the mode and the frequency of consumption which created the accoutumance or the dependence with the product. one can thus think that it is the consumer ( through his modes of consumption ), more than the product which determines which substance will be, for him, a drug. a system of regulation of the production, trade and consumption of drugs were set up during the 20th century. the rules enacted by the states take account of the political, social and medical implications of the drug taking and determine the reglementation of their use or their prohibition. a policy of prohibition more or less generalized was also installation for the products stupefiant s. the legislation installation thus makes it possible it also to specify the concept of drug. etymologythe etymology of the term is vague. for the majority of the modern works. some think that this word could also come from the hebrew “ rakab ” ( perfume ) or of the arab “ drawa ” ( ball of corn ). the taking into account of several parameters makes it possible to better determine the concept of drug. for pierre - arnaud chouvy, “ drug is first of all a product of origin animal e, vegetal e or synthetique, which, introduced into the organization by some means that it is, has on this one of the effects biodynamic, and who can, in certain cases, to create a more or less serious accoutumance ”. a third element making it possible to define a drug are the standards imposed by a given company. these three elements make it possible to apprehend drug like a phenomenon of societe. this difference in approach of


2. a look at some fractal application programs 3. extensions of iteration a presentation of various lengths can be developed by varying the amount of emphasis given to the different sections of the outline. the introduction is a good place to stress the need to include more than the computation component of mathematics and to identify the motivating aspects of teaching through applications. looking at examples of mathematical models and, also, looking at problems dealing with " real world " data can renew a teacher ' s interest in reaching beyond the teaching of computation and abstract procedures. to understand fractals, and eventually, to understand dynamical systems, requires some expertise with iteration. the number of examples of iteration and the complexity of the examples you select will depend on the length of the presentation and the type of audience. the length of the presentation will also determine how many fractals can be demonstrated and how much hands - on work can be done. the availability of computers or graphing calculators will extend the possibilities for demonstrations with fractals. even though the 1993 woodrow wilson national fellowship foundation math institute focused considerable amounts of time on the study of dynamical systems beyond fractals, this workshop outline is directed toward developing background concepts. in fact, most of the problems in this book on change can be used with students who have a good working knowledge of algebra ii or pre - calculus. this book, combined with the technology now available, provides a new way of exploring problems that prior to this may have been purely in the venue of a research mathematician. it is exciting to realize that the knowledge and resources for investigating a " frontier " of mathematics are now in the reach of many high school students. all the resources alluded to in this project are listed in the bibliography at the end of the 1993 wwnff math institute book on change.


libbrecht, k. g. and black, e. d. and hirata, c. m. ( 2003 ) a basic lock - in amplifier experiment for the undergraduate laboratory. american journal of physics, 71 ( 11 ). pp. 1208 - 1213. issn 0002 - 9505 http : / / resolver. caltech. edu / caltechauthors : libajp03 - published version see usage policy. use this persistent url to link to this item : http : / / resolver. caltech. edu / caltechauthors : libajp03 we describe a basic experiment for the undergraduate laboratory that demonstrates aspects of both, the science and the art of precision electronic measurements. the essence of the experiment is to measure the resistance of a small length of brass - wire to high accuracy using a simple voltage divider and a lock - in amplifier. by performing the measurement at different frequencies and different drive currents, one observes various random noise sources and systematic measurement effects. | additional information : | | © 2003 american association of physics teachers. received 9 august 2002 ; accepted 9 april 2003. | | usage policy : | | no commercial reproduction, distribution, display or performance rights in this work are provided. | | deposited by : | | tony diaz | | deposited on : | | 30 jan 2009 00 : 40 | | last modified : | | 26 dec 2012 10 : 38 | repository staff only : item control page


the large hadron collider ( lhc ) is the world ’ s largest and most powerful particle accelerator. it first started up on 10 september 2008, and remains the latest addition to cern ’ s accelerator complex. the lhc consists of a 27 - kilometre ring of superconducting magnets with a number of accelerating structures to boost the energy of the particles along the way. inside the accelerator, two high - energy particle beams travel at close to the speed of light before they are made to collide. the beams travel in opposite directions in separate beam pipes – two tubes kept at ultrahigh vacuum. they are guided around the accelerator ring by a strong magnetic field maintained by superconducting electromagnets. the electromagnets are built from coils of special electric cable that operates in a superconducting state, efficiently conducting electricity without resistance or loss of energy. this requires chilling the magnets to ‑ 271. 3°c – a temperature colder than outer space. for this reason, much of the accelerator is connected to a distribution system of liquid helium, which cools the magnets, as well as to other supply services. thousands of magnets of different varieties and sizes are used to direct the beams around the accelerator. these include 1232 dipole magnets 15 metres in length which bend the beams, and 392 quadrupole magnets, each 5 – 7 metres long, which focus the beams. just prior to collision, another type of magnet is used to " squeeze " the particles closer together to increase the chances of collisions. the particles are so tiny that the task of making them collide is akin to firing two needles 10 kilometres apart with such precision that they meet halfway! all the controls for the accelerator, its services and technical infrastructure are housed under one roof at the cern control centre. from here, the beams inside the lhc are made to collide at four locations around the accelerator ring, corresponding to the positions of four particle detectors – atlas, cms, alice and lhcb.


lives : neuronal and organismal lifespans decoupled mar 27, 2013 | 4. 9 / 5 ( 8 ) | 0 - sizing things up : the evolutionary neurobiology of scale invariance feb 28, 2013 | 4. 8 / 5 ( 10 ) | 14 force between two concentric solenoids 2 hours ago imagine a finite length solenoid with outer radius r1 and inner radius r2. this solenoid has a time - varying current going though it. this solenoid is... synchrotron, question about insertion devices and electron velocity 2 hours ago when an electron enters an insertion device ( wiggler and undulator ) from the storage ring in a synchrotron the tangential velocity is equal to the... equating differentials = > equating coefficients 4 hours ago hi all, in thermodynamics one often has equations like a dx + b dy = ∂f / ∂x dx + ∂f / ∂y dy from which follows a = ∂f / ∂x b = ∂f / ∂y the idea behind a reverse shock 10 hours ago so in a supernova explosion for example ( 5th slide ) http : / / www. astro. princeton. edu / ~ burrows / classes / 541 / blastwaveschisari. pdf ambient medium is... guass ' s law for a charge distribution 10 hours ago first, this is not a homework question, just something i ' ve been confused about for some time. i understand how to use guass ' s law in many ways but... 11 hours ago hello : ) i ' m new to this forum, so excuse me for my straightforwardness ; ) i ' m working on my bachelor work and i can ' t find a solution. i ' m writing... - more from physics forums - classical physics more news stories kate o ' reilly ' s spring allergy survival kit includes the usual stuff - nasal sprays, allergy pills and a box of tissues. this season, she ' s added a new weapon to her line of defense : an app on her smartphone. immunology may 24, 2013 | not rated yet | 0 biological processes are generally based on events at the molecular and cellular level. to understand what happens in the course of infections, diseases or normal bodily functions, scientists would need to... immunology may 24, 2013 | 5 / 5 ( 5 ) | 0 | ( medical xp


physics by aristotle public domain english translation by r. p. hardie and r. k. gaye when the objects of an inquiry, in any department, have principles, conditions, or elements, it is through acquaintance with these that knowledge, that is to say scientific knowledge, is attained. for we do not think that we know a thing until we are acquainted with its primary conditions or first principles, and have carried our analysis as far as its simplest elements. plainly therefore in the science of nature, as in other branches of study, our first task will be to try to determine what relates to its principles. the natural way of doing this is to start from the things which are more knowable and obvious to us and proceed towards those which are clearer and more knowable by nature ; for the same things are not ' knowable relatively to us ' and ' knowable ' without qualification. so in the present inquiry we must follow this method and advance from what is more obscure by nature, but clearer to us, towards what is more clear and more knowable by nature. now what is to us plain and obvious at first is rather confused masses, the elements and principles of which become known to us later by analysis. thus we must advance from generalities to particulars ; for it is a whole that is best known to sense - perception, and a generality is a kind of whole, comprehending many things within it, like parts. much the same thing happens in the relation of the name to the formula. a name, e. g. ' round ', means vaguely a sort of whole : its definition analyses this into its particular senses. similarly a child begins by calling all men ' father ', and all women ' mother ', but later on distinguishes each of them. the principles in question must be either ( a ) one or ( b ) more than one. if ( a ) one, it must be either ( i ) motionless, as parmenides and melissus assert, or ( ii ) in motion, as the physicists hold, some declaring air to be the first principle, others water. if ( b ) more than one, then either ( i ) a finite or ( ii ) an infinite plurality. if ( i ) finite ( but more than one ), then either two or three or four or some other number. if ( ii ) infinite, then either as democritus believed one in kind, but differing in shape or form ; or different in kind and even contrary. a similar inquiry is


, then either two or three or four or some other number. if ( ii ) infinite, then either as democritus believed one in kind, but differing in shape or form ; or different in kind and even contrary. a similar inquiry is made by those who inquire into the number of existents : for they inquire whether the ultimate constituents of existing things are one or many, and if many, whether a finite or an infinite plurality. so they too are inquiring whether the principle or element is one or many. now to investigate whether being is one and motionless is not a contribution to the science of nature. for just as the geometer has nothing more to say to one who denies the principles of his science - this being a question for a different science or for or common to all - so a man investigating principles cannot argue with one who denies their existence. for if being is just one, and one in the way mentioned, there is a principle no longer, since a principle must be the principle of some thing or things. to inquire therefore whether being is one in this sense would be like arguing against any other position maintained for the sake of argument ( such as the heraclitean thesis, or such a thesis as that being is one man ) or like refuting a merely contentious argument - a description which applies to the arguments both of melissus and of parmenides : their premisses are false and their conclusions do not follow. or rather the argument of melissus is gross and palpable and offers no difficulty at all : accept one ridiculous proposition and the rest follows - a simple enough proceeding. we physicists, on the other hand, must take for granted that the things that exist by nature are, either all or some of them, in motion which is indeed made plain by induction. moreover, no man of science is bound to solve every kind of difficulty that may be raised, but only as many as are drawn falsely from the principles of the science : it is not our business to refute those that do not arise in this way : just as it is the duty of the geometer to refute the squaring of the circle by means of segments, but it is not his duty to refute antiphon ' s proof. at the same time the holders of the theory of which we are speaking do incidentally raise physical questions, though nature is not their subject : so it will perhaps be as well to spend a few words on them, especially as the inquiry


s proof. at the same time the holders of the theory of which we are speaking do incidentally raise physical questions, though nature is not their subject : so it will perhaps be as well to spend a few words on them, especially as the inquiry is not without scientific interest. the most pertinent question with which to begin will be this : in what sense is it asserted that all things are one? for ' is ' is used in many senses. do they mean that all things ' are ' substance or quantities or qualities? and, further, are all things one substance - one man, one horse, or one soul - or quality and that one and the same - white or hot or something of the kind? these are all very different doctrines and all impossible to maintain. for if both substance and quantity and quality are, then, whether these exist independently of each other or not, being will be many. if on the other hand it is asserted that all things are quality or quantity, then, whether substance exists or not, an absurdity results, if the impossible can properly be called absurd. for none of the others can exist independently : substance alone is independent : for everything is predicated of substance as subject. now melissus says that being is infinite. it is then a quantity. for the infinite is in the category of quantity, whereas substance or quality or affection cannot be infinite except through a concomitant attribute, that is, if at the same time they are also quantities. for to define the infinite you must use quantity in your formula, but not substance or quality. if then being is both substance and quantity, it is two, not one : if only substance, it is not infinite and has no magnitude ; for to have that it will have to be a quantity. again, ' one ' itself, no less than ' being ', is used in many senses, so we must consider in what sense the word is used when it is said that the all is one. now we say that ( a ) the continuous is one or that ( b ) the indivisible is one, or ( c ) things are said to be ' one ', when their essence is one and the same, as ' liquor ' and ' drink '. if ( a ) their one is one in the sense of continuous, it is many, for the continuous is divisible ad infinitum. there is, indeed, a difficulty about part and whole, perhaps not relevant to the present argument, yet des


- being, but in the sense that it is not at all. hence ' substance ' is not ; for it is true to say that it is white, which we found to mean not - being. if to avoid this we say that even ' white ' means substance, it follows that ' being ' has more than one meaning. in particular, then, being will not have magnitude, if it is substance. for each of the two parts must he in a different sense. ( 2 ) substance is plainly divisible into other substances, if we consider the mere nature of a definition. for instance, if ' man ' is a substance, ' animal ' and ' biped ' must also be substances. for if not substances, they must be attributes - and if attributes, attributes either of ( a ) man or of ( b ) some other subject. but neither is possible. ( a ) an attribute is either that which may or may not belong to the subject or that in whose definition the subject of which it is an attribute is involved. thus ' sitting ' is an example of a separable attribute, while ' snubness ' contains the definition of ' nose ', to which we attribute snubness. further, the definition of the whole is not contained in the definitions of the contents or elements of the definitory formula ; that of ' man ' for instance in ' biped ', or that of ' white man ' in ' white '. if then this is so, and if ' biped ' is supposed to be an attribute of ' man ', it must be either separable, so that ' man ' might possibly not be ' biped ', or the definition of ' man ' must come into the definition of ' biped ' - which is impossible, as the converse is the case. ( b ) if, on the other hand, we suppose that ' biped ' and ' animal ' are attributes not of man but of something else, and are not each of them a substance, then ' man ' too will be an attribute of something else. but we must assume that substance is not the attribute of anything, that the subject of which both ' biped ' and ' animal ' and each separately are predicated is the subject also of the complex ' biped animal '. are we then to say that the all is composed of indivisible substances? some thinkers did, in point of fact, give way to both arguments. to the argument that all things are one if being


the complex ' biped animal '. are we then to say that the all is composed of indivisible substances? some thinkers did, in point of fact, give way to both arguments. to the argument that all things are one if being means one thing, they conceded that not - being is ; to that from bisection, they yielded by positing atomic magnitudes. but obviously it is not true that if being means one thing, and cannot at the same time mean the contradictory of this, there will be nothing which is not, for even if what is not cannot be without qualification, there is no reason why it should not be a particular not - being. to say that all things will be one, if there is nothing besides being itself, is absurd. for who understands ' being itself ' to be anything but a particular substance? but if this is so, there is nothing to prevent there being many beings, as has been said. it is, then, clearly impossible for being to be one in this sense. the physicists on the other hand have two modes of explanation. the first set make the underlying body one either one of the three or something else which is denser than fire and rarer than air then generate everything else from this, and obtain multiplicity by condensation and rarefaction. now these are contraries, which may be generalized into ' excess and defect '. ( compare plato ' s ' great and small ' - except that he make these his matter, the one his form, while the others treat the one which underlies as matter and the contraries as differentiae, i. e. forms ). the second set assert that the contrarieties are contained in the one and emerge from it by segregation, for example anaximander and also all those who assert that ' what is ' is one and many, like empedocles and anaxagoras ; for they too produce other things from their mixture by segregation. these differ, however, from each other in that the former imagines a cycle of such changes, the latter a single series. anaxagoras again made both his ' homceomerous ' substances and his contraries infinite in multitude, whereas empedocles posits only the so - called elements. the theory of anaxagoras that the principles are infinite in multitude was probably due to his acceptance of the common opinion of the physicists that nothing comes into being from not - being. for this is the reason why they


so - called elements. the theory of anaxagoras that the principles are infinite in multitude was probably due to his acceptance of the common opinion of the physicists that nothing comes into being from not - being. for this is the reason why they use the phrase ' all things were together ' and the coming into being of such and such a kind of thing is reduced to change of quality, while some spoke of combination and separation. moreover, the fact that the contraries proceed from each other led them to the conclusion. the one, they reasoned, must have already existed in the other ; for since everything that comes into being must arise either from what is or from what is not, and it is impossible for it to arise from what is not ( on this point all the physicists agree ), they thought that the truth of the alternative necessarily followed, namely that things come into being out of existent things, i. e. out of things already present, but imperceptible to our senses because of the smallness of their bulk. so they assert that everything has been mixed in every. thing, because they saw everything arising out of everything. but things, as they say, appear different from one another and receive different names according to the nature of the particles which are numerically predominant among the innumerable constituents of the mixture. for nothing, they say, is purely and entirely white or black or sweet, bone or flesh, but the nature of a thing is held to be that of which it contains the most. now ( 1 ) the infinite qua infinite is unknowable, so that what is infinite in multitude or size is unknowable in quantity, and what is infinite in variety of kind is unknowable in quality. but the principles in question are infinite both in multitude and in kind. therefore it is impossible to know things which are composed of them ; for it is when we know the nature and quantity of its components that we suppose we know a complex. further ( 2 ) if the parts of a whole may be of any size in the direction either of greatness or of smallness ( by ' parts ' i mean components into which a whole can be divided and which are actually present in it ), it is necessary that the whole thing itself may be of any size. clearly, therefore, since it is impossible for an animal or plant to be indefinitely big or small, neither can its parts be such, or the whole will be the same. but flesh, bone, and the like


, for instance, from black and white. everything, therefore, that comes to be by a natural process is either a contrary or a product of contraries. up to this point we have practically had most of the other writers on the subject with us, as i have said already : for all of them identify their elements, and what they call their principles, with the contraries, giving no reason indeed for the theory, but contrained as it were by the truth itself. they differ, however, from one another in that some assume contraries which are more primary, others contraries which are less so : some those more knowable in the order of explanation, others those more familiar to sense. for some make hot and cold, or again moist and dry, the conditions of becoming ; while others make odd and even, or again love and strife ; and these differ from each other in the way mentioned. hence their principles are in one sense the same, in another different ; different certainly, as indeed most people think, but the same inasmuch as they are analogous ; for all are taken from the same table of columns, some of the pairs being wider, others narrower in extent. in this way then their theories are both the same and different, some better, some worse ; some, as i have said, take as their contraries what is more knowable in the order of explanation, others what is more familiar to sense. ( the universal is more knowable in the order of explanation, the particular in the order of sense : for explanation has to do with the universal, sense with the particular. ) ' the great and the small ', for example, belong to the former class, ' the dense and the rare ' to the latter. it is clear then that our principles must be contraries. the next question is whether the principles are two or three or more in number. one they cannot be, for there cannot be one contrary. nor can they be innumerable, because, if so, being will not be knowable : and in any one genus there is only one contrariety, and substance is one genus : also a finite number is sufficient, and a finite number, such as the principles of empedocles, is better than an infinite multitude ; for empedocles professes to obtain from his principles all that anaxagoras obtains from his innumerable principles. lastly, some contraries are more primary than others, and some arise from others - for example sweet and bitter, white


empedocles professes to obtain from his principles all that anaxagoras obtains from his innumerable principles. lastly, some contraries are more primary than others, and some arise from others - for example sweet and bitter, white and black - whereas the principles must always remain principles. this will suffice to show that the principles are neither one nor innumerable. granted, then, that they are a limited number, it is plausible to suppose them more than two. for it is difficult to see how either density should be of such a nature as to act in any way on rarity or rarity on density. the same is true of any other pair of contraries ; for love does not gather strife together and make things out of it, nor does strife make anything out of love, but both act on a third thing different from both. some indeed assume more than one such thing from which they construct the world of nature. other objections to the view that it is not necessary to assume a third principle as a substratum may be added. ( 1 ) we do not find that the contraries constitute the substance of any thing. but what is a first principle ought not to be the predicate of any subject. if it were, there would be a principle of the supposed principle : for the subject is a principle, and prior presumably to what is predicated of it. again ( 2 ) we hold that a substance is not contrary to another substance. how then can substance be derived from what are not substances? or how can non - substances be prior to substance? if then we accept both the former argument and this one, we must, to preserve both, assume a third somewhat as the substratum of the contraries, such as is spoken of by those who describe the all as one nature - water or fire or what is intermediate between them. what is intermediate seems preferable ; for fire, earth, air, and water are already involved with pairs of contraries. there is, therefore, much to be said for those who make the underlying substance different from these four ; of the rest, the next best choice is air, as presenting sensible differences in a less degree than the others ; and after air, water. all, however, agree in this, that they differentiate their one by means of the contraries, such as density and rarity and more and less, which may of course be generalized, as has already been said into excess and defect. indeed this doctrine too ( that the one


this, that they differentiate their one by means of the contraries, such as density and rarity and more and less, which may of course be generalized, as has already been said into excess and defect. indeed this doctrine too ( that the one and excess and defect are the principles of things ) would appear to be of old standing, though in different forms ; for the early thinkers made the two the active and the one the passive principle, whereas some of the more recent maintain the reverse. to suppose then that the elements are three in number would seem, from these and similar considerations, a plausible view, as i said before. on the other hand, the view that they are more than three in number would seem to be untenable. for the one substratum is sufficient to be acted on ; but if we have four contraries, there will be two contrarieties, and we shall have to suppose an intermediate nature for each pair separately. if, on the other hand, the contrarieties, being two, can generate from each other, the second contrariety will be superfluous. moreover, it is impossible that there should be more than one primary contrariety. for substance is a single genus of being, so that the principles can differ only as prior and posterior, not in genus ; in a single genus there is always a single contrariety, all the other contrarieties in it being held to be reducible to one. it is clear then that the number of elements is neither one nor more than two or three ; but whether two or three is, as i said, a question of considerable difficulty. we will now give our own account, approaching the question first with reference to becoming in its widest sense : for we shall be following the natural order of inquiry if we speak first of common characteristics, and then investigate the characteristics of special cases. we say that one thing comes to be from another thing, and one sort of thing from another sort of thing, both in the case of simple and of complex things. i mean the following. we can say ( 1 ) ' man becomes musical ', ( 2 ) what is ' not - musical becomes musical ', or ( 3 ), the ' not - musical man becomes a musical man '. now what becomes in ( 1 ) and ( 2 ) - ' man ' and ' not musical ' - i call simple, and what each becomes - ' musical ' - simple also. but when ( 3 ) we say the ' not - musical man becomes a


the number of the principles of natural objects which are subject to generation, and how the number is reached : and it is clear that there must be a substratum for the contraries, and that the contraries must be two. ( yet in another way of putting it this is not necessary, as one of the contraries will serve to effect the change by its successive absence and presence. ) the underlying nature is an object of scientific knowledge, by an analogy. for as the bronze is to the statue, the wood to the bed, or the matter and the formless before receiving form to any thing which has form, so is the underlying nature to substance, i. e. the ' this ' or existent. this then is one principle ( though not one or existent in the same sense as the ' this ' ), and the definition was one as we agreed ; then further there is its contrary, the privation. in what sense these are two, and in what sense more, has been stated above. briefly, we explained first that only the contraries were principles, and later that a substratum was indispensable, and that the principles were three ; our last statement has elucidated the difference between the contraries, the mutual relation of the principles, and the nature of the substratum. whether the form or the substratum is the essential nature of a physical object is not yet clear. but that the principles are three, and in what sense, and the way in which each is a principle, is clear. so much then for the question of the number and the nature of the principles. we will now proceed to show that the difficulty of the early thinkers, as well as our own, is solved in this way alone. the first of those who studied science were misled in their search for truth and the nature of things by their inexperience, which as it were thrust them into another path. so they say that none of the things that are either comes to be or passes out of existence, because what comes to be must do so either from what is or from what is not, both of which are impossible. for what is cannot come to be ( because it is already ), and from what is not nothing could have come to be ( because something must be present as a substratum ). so too they exaggerated the consequence of this, and went so far as to deny even the existence of a plurality of things, maintaining that only being itself is. such then was


comes to be from being, and that being does not come to be except in a qualified sense. in that way, however, it does, just as animal might come to be from animal, and an animal of a certain kind from an animal of a certain kind. thus, suppose a dog to come to be from a horse. the dog would then, it is true, come to be from animal ( as well as from an animal of a certain kind ) but not as animal, for that is already there. but if anything is to become an animal, not in a qualified sense, it will not be from animal : and if being, not from being - nor from not - being either, for it has been explained that by ' from not being ' we mean from not - being qua not - being. note further that we do not subvert the principle that everything either is or is not. this then is one way of solving the difficulty. another consists in pointing out that the same things can be explained in terms of potentiality and actuality. but this has been done with greater precision elsewhere. so, as we said, the difficulties which constrain people to deny the existence of some of the things we mentioned are now solved. for it was this reason which also caused some of the earlier thinkers to turn so far aside from the road which leads to coming to be and passing away and change generally. if they had come in sight of this nature, all their ignorance would have been dispelled. others, indeed, have apprehended the nature in question, but not adequately. in the first place they allow that a thing may come to be without qualification from not being, accepting on this point the statement of parmenides. secondly, they think that if the substratum is one numerically, it must have also only a single potentiality - which is a very different thing. now we distinguish matter and privation, and hold that one of these, namely the matter, is not - being only in virtue of an attribute which it has, while the privation in its own nature is not - being ; and that the matter is nearly, in a sense is, substance, while the privation in no sense is. they, on the other hand, identify their great and small alike with not being, and that whether they are taken together as one or separately. their triad is therefore of quite a different kind from ours. for they got so far as to see that there must be some underlying nature,


identify their great and small alike with not being, and that whether they are taken together as one or separately. their triad is therefore of quite a different kind from ours. for they got so far as to see that there must be some underlying nature, but they make it one - for even if one philosopher makes a dyad of it, which he calls great and small, the effect is the same, for he overlooked the other nature. for the one which persists is a joint cause, with the form, of what comes to be - a mother, as it were. but the negative part of the contrariety may often seem, if you concentrate your attention on it as an evil agent, not to exist at all. for admitting with them that there is something divine, good, and desirable, we hold that there are two other principles, the one contrary to it, the other such as of its own nature to desire and yearn for it. but the consequence of their view is that the contrary desires its wtextinction. yet the form cannot desire itself, for it is not defective ; nor can the contrary desire it, for contraries are mutually destructive. the truth is that what desires the form is matter, as the female desires the male and the ugly the beautiful - only the ugly or the female not per se but per accidens. the matter comes to be and ceases to be in one sense, while in another it does not. as that which contains the privation, it ceases to be in its own nature, for what ceases to be - the privation - is contained within it. but as potentiality it does not cease to be in its own nature, but is necessarily outside the sphere of becoming and ceasing to be. for if it came to be, something must have existed as a primary substratum from which it should come and which should persist in it ; but this is its own special nature, so that it will be before coming to be. ( for my definition of matter is just this - the primary substratum of each thing, from which it comes to be without qualification, and which persists in the result. ) and if it ceases to be it will pass into that at the last, so it will have ceased to be before ceasing to be. the accurate determination of the first principle in respect of form, whether it is one or many and what it is or what they are, is the province of the primary type of science ; so these


have ceased to be before ceasing to be. the accurate determination of the first principle in respect of form, whether it is one or many and what it is or what they are, is the province of the primary type of science ; so these questions may stand over till then. but of the natural, i. e. perishable, forms we shall speak in the expositions which follow. the above, then, may be taken as sufficient to establish that there are principles and what they are and how many there are. now let us make a fresh start and proceed. of things that exist, some exist by nature, some from other causes. ' by nature ' the animals and their parts exist, and the plants and the simple bodies ( earth, fire, air, water ) - for we say that these and the like exist ' by nature '. all the things mentioned present a feature in which they differ from things which are not constituted by nature. each of them has within itself a principle of motion and of stationariness ( in respect of place, or of growth and decrease, or by way of alteration ). on the other hand, a bed and a coat and anything else of that sort, qua receiving these designations i. e. in so far as they are products of art - have no innate impulse to change. but in so far as they happen to be composed of stone or of earth or of a mixture of the two, they do have such an impulse, and just to that extent which seems to indicate that nature is a source or cause of being moved and of being at rest in that to which it belongs primarily, in virtue of itself and not in virtue of a concomitant attribute. i say ' not in virtue of a concomitant attribute ', because ( for instance ) a man who is a doctor might cure himself. nevertheless it is not in so far as he is a patient that he possesses the art of medicine : it merely has happened that the same man is doctor and patient - and that is why these attributes are not always found together. so it is with all other artificial products. none of them has in itself the source of its own production. but while in some cases ( for instance houses and the other products of manual labour ) that principle is in something else external to the thing, in others those which may cause a change in themselves in virtue of a concomitant attribute - it lies in the things themselves ( but not in virtue of what they are ). '


their nature and essence. consequently some assert earth, others fire or air or water or some or all of these, to be the nature of the things that are. for whatever any one of them supposed to have this character - whether one thing or more than one thing - this or these he declared to be the whole of substance, all else being its affections, states, or dispositions. every such thing they held to be eternal ( for it could not pass into anything else ), but other things to come into being and cease to be times without number. this then is one account of ' nature ', namely that it is the immediate material substratum of things which have in themselves a principle of motion or change. another account is that ' nature ' is the shape or form which is specified in the definition of the thing. for the word ' nature ' is applied to what is according to nature and the natural in the same way as ' art ' is applied to what is artistic or a work of art. we should not say in the latter case that there is anything artistic about a thing, if it is a bed only potentially, not yet having the form of a bed ; nor should we call it a work of art. the same is true of natural compounds. what is potentially flesh or bone has not yet its own ' nature ', and does not exist until it receives the form specified in the definition, which we name in defining what flesh or bone is. thus in the second sense of ' nature ' it would be the shape or form ( not separable except in statement ) of things which have in themselves a source of motion. ( the combination of the two, e. g. man, is not ' nature ' but ' by nature ' or ' natural '. ) the form indeed is ' nature ' rather than the matter ; for a thing is more properly said to be what it is when it has attained to fulfilment than when it exists potentially. again man is born from man, but not bed from bed. that is why people say that the figure is not the nature of a bed, but the wood is - if the bed sprouted not a bed but wood would come up. but even if the figure is art, then on the same principle the shape of man is his nature. for man is born from man. we also speak of a thing ' s nature as being exhibited in the process of growth by which its nature is attained. the ' nature ' in this sense is not like ' doctor


shape of man is his nature. for man is born from man. we also speak of a thing ' s nature as being exhibited in the process of growth by which its nature is attained. the ' nature ' in this sense is not like ' doctoring ', which leads not to the art of doctoring but to health. doctoring must start from the art, not lead to it. but it is not in this way that nature ( in the one sense ) is related to nature ( in the other ). what grows qua growing grows from something into something. into what then does it grow? not into that from which it arose but into that to which it tends. the shape then is nature. ' shape ' and ' nature ', it should be added, are in two senses. for the privation too is in a way form. but whether in unqualified coming to be there is privation, i. e. a contrary to what comes to be, we must consider later. we have distinguished, then, the different ways in which the term ' nature ' is used. the next point to consider is how the mathematician differs from the physicist. obviously physical bodies contain surfaces and volumes, lines and points, and these are the subject - matter of mathematics. further, is astronomy different from physics or a department of it? it seems absurd that the physicist should be supposed to know the nature of sun or moon, but not to know any of their essential attributes, particularly as the writers on physics obviously do discuss their shape also and whether the earth and the world are spherical or not. now the mathematician, though he too treats of these things, nevertheless does not treat of them as the limits of a physical body ; nor does he consider the attributes indicated as the attributes of such bodies. that is why he separates them ; for in thought they are separable from motion, and it makes no difference, nor does any falsity result, if they are separated. the holders of the theory of forms do the same, though they are not aware of it ; for they separate the objects of physics, which are less separable than those of mathematics. this becomes plain if one tries to state in each of the two cases the definitions of the things and of their attributes. ' odd ' and ' even ', ' straight ' and ' curved ', and likewise ' number ', ' line ', and ' figure ', do not involve motion ; not so ' flesh ' and ' bone ' and ' man ' - these are


' and ' even ', ' straight ' and ' curved ', and likewise ' number ', ' line ', and ' figure ', do not involve motion ; not so ' flesh ' and ' bone ' and ' man ' - these are defined like ' snub nose ', not like ' curved '. similar evidence is supplied by the more physical of the branches of mathematics, such as optics, harmonics, and astronomy. these are in a way the converse of geometry. while geometry investigates physical lines but not qua physical, optics investigates mathematical lines, but qua physical, not qua mathematical. since ' nature ' has two senses, the form and the matter, we must investigate its objects as we would the essence of snubness. that is, such things are neither independent of matter nor can be defined in terms of matter only. here too indeed one might raise a difficulty. since there are two natures, with which is the physicist concerned? or should he investigate the combination of the two? but if the combination of the two, then also each severally. does it belong then to the same or to different sciences to know each severally? if we look at the ancients, physics would to be concerned with the matter. ( it was only very slightly that empedocles and democritus touched on the forms and the essence. ) but if on the other hand art imitates nature, and it is the part of the same discipline to know the form and the matter up to a point ( e. g. the doctor has a knowledge of health and also of bile and phlegm, in which health is realized, and the builder both of the form of the house and of the matter, namely that it is bricks and beams, and so forth ) : if this is so, it would be the part of physics also to know nature in both its senses. again, ' that for the sake of which ', or the end, belongs to the same department of knowledge as the means. but the nature is the end or ' that for the sake of which '. for if a thing undergoes a continuous change and there is a stage which is last, this stage is the end or ' that for the sake of which '. ( that is why the poet was carried away into making an absurd statement when he said ' he has the end for the sake of which he was born '. for not every stage that is last claims to be an end, but only that which


their principles, we may try to refer to these principles each of our problems. in one sense, then, ( 1 ) that out of which a thing comes to be and which persists, is called ' cause ', e. g. the bronze of the statue, the silver of the bowl, and the genera of which the bronze and the silver are species. in another sense ( 2 ) the form or the archetype, i. e. the statement of the essence, and its genera, are called ' causes ' ( e. g. of the octave the relation of 2 : 1, and generally number ), and the parts in the definition. again ( 3 ) the primary source of the change or coming to rest ; e. g. the man who gave advice is a cause, the father is cause of the child, and generally what makes of what is made and what causes change of what is changed. again ( 4 ) in the sense of end or ' that for the sake of which ' a thing is done, e. g. health is the cause of walking about. ( ' why is he walking about? ' we say. ' to be healthy ', and, having said that, we think we have assigned the cause. ) the same is true also of all the intermediate steps which are brought about through the action of something else as means towards the end, e. g. reduction of flesh, purging, drugs, or surgical instruments are means towards health. all these things are ' for the sake of ' the end, though they differ from one another in that some are activities, others instruments. this then perhaps exhausts the number of ways in which the term ' cause ' is used. as the word has several senses, it follows that there are several causes of the same thing not merely in virtue of a concomitant attribute ), e. g. both the art of the sculptor and the bronze are causes of the statue. these are causes of the statue qua statue, not in virtue of anything else that it may be - only not in the same way, the one being the material cause, the other the cause whence the motion comes. some things cause each other reciprocally, e. g. hard work causes fitness and vice versa, but again not in the same way, but the one as end, the other as the origin of change. further the same thing is the cause of contrary results. for that which by its presence brings about one result is sometimes blamed for


point is the starting - point of the reasoning only, as there is no action. if then there is to be a house, such - and - such things must be made or be there already or exist, or generally the matter relative to the end, bricks and stones if it is a house. but the end is not due to these except as the matter, nor will it come to exist because of them. yet if they do not exist at all, neither will the house, or the saw - the former in the absence of stones, the latter in the absence of iron - just as in the other case the premisses will not be true, if the angles of the triangle are not equal to two right angles. the necessary in nature, then, is plainly what we call by the name of matter, and the changes in it. both causes must be stated by the physicist, but especially the end ; for that is the cause of the matter, not vice versa ; and the end is ' that for the sake of which ', and the beginning starts from the definition or essence ; as in artificial products, since a house is of such - and - such a kind, certain things must necessarily come to be or be there already, or since health is this, these things must necessarily come to be or be there already. similarly if man is this, then these ; if these, then those. perhaps the necessary is present also in the definition. for if one defines the operation of sawing as being a certain kind of dividing, then this cannot come about unless the saw has teeth of a certain kind ; and these cannot be unless it is of iron. for in the definition too there are some parts that are, as it were, its matter. nature has been defined as a ' principle of motion and change ', and it is the subject of our inquiry. we must therefore see that we understand the meaning of ' motion ' ; for if it were unknown, the meaning of ' nature ' too would be unknown. when we have determined the nature of motion, our next task will be to attack in the same way the terms which are involved in it. now motion is supposed to belong to the class of things which are continuous ; and the infinite presents itself first in the continuous - that is how it comes about that ' infinite ' is often used in definitions of the continuous ( ' what is infinitely divisible is continuous ' ). besides these, place, void, and time are thought to be necessary conditions of motion. clearly,


is how it comes about that ' infinite ' is often used in definitions of the continuous ( ' what is infinitely divisible is continuous ' ). besides these, place, void, and time are thought to be necessary conditions of motion. clearly, then, for these reasons and also because the attributes mentioned are common to, and coextensive with, all the objects of our science, we must first take each of them in hand and discuss it. for the investigation of special attributes comes after that of the common attributes. to begin then, as we said, with motion. we may start by distinguishing ( 1 ) what exists in a state of fulfilment only, ( 2 ) what exists as potential, ( 3 ) what exists as potential and also in fulfilment - one being a ' this ', another ' so much ', a third ' such ', and similarly in each of the other modes of the predication of being. further, the word ' relative ' is used with reference to ( 1 ) excess and defect, ( 2 ) agent and patient and generally what can move and what can be moved. for ' what can cause movement ' is relative to ' what can be moved ', and vice versa. again, there is no such thing as motion over and above the things. it is always with respect to substance or to quantity or to quality or to place that what changes changes. but it is impossible, as we assert, to find anything common to these which is neither ' this ' nor quantum nor quale nor any of the other predicates. hence neither will motion and change have reference to something over and above the things mentioned, for there is nothing over and above them. now each of these belongs to all its subjects in either of two ways : namely ( 1 ) substance - the one is positive form, the other privation ; ( 2 ) in quality, white and black ; ( 3 ) in quantity, complete and incomplete ; ( 4 ) in respect of locomotion, upwards and downwards or light and heavy. hence there are as many types of motion or change as there are meanings of the word ' is '. we have now before us the distinctions in the various classes of being between what is full real and what is potential. def. the fulfilment of what exists potentially, in so far as it exists potentially, is motion - namely, of what is alterable qua alterable, alteration : of what can be increased and its opposite what can be decreased (


def. the fulfilment of what exists potentially, in so far as it exists potentially, is motion - namely, of what is alterable qua alterable, alteration : of what can be increased and its opposite what can be decreased ( there is no common name ), increase and decrease : of what can come to be and can pass away, coming to he and passing away : of what can be carried along, locomotion. examples will elucidate this definition of motion. when the buildable, in so far as it is just that, is fully real, it is being built, and this is building. similarly, learning, doctoring, rolling, leaping, ripening, ageing. the same thing, if it is of a certain kind, can be both potential and fully real, not indeed at the same time or not in the same respect, but e. g. potentially hot and actually cold. hence at once such things will act and be acted on by one another in many ways : each of them will be capable at the same time of causing alteration and of being altered. hence, too, what effects motion as a physical agent can be moved : when a thing of this kind causes motion, it is itself also moved. this, indeed, has led some people to suppose that every mover is moved. but this question depends on another set of arguments, and the truth will be made clear later. is possible for a thing to cause motion, though it is itself incapable of being moved. it is the fulfilment of what is potential when it is already fully real and operates not as itself but as movable, that is motion. what i mean by ' as ' is this : bronze is potentially a statue. but it is not the fulfilment of bronze as bronze which is motion. for ' to be bronze ' and ' to be a certain potentiality ' are not the same. if they were identical without qualification, i. e. in definition, the fulfilment of bronze as bronze would have been motion. but they are not the same, as has been said. ( this is obvious in contraries. ' to be capable of health ' and ' to be capable of illness ' are not the same, for if they were there would be no difference between being ill and being well. yet the subject both of health and of sickness - whether it is humour or blood - is one and the same. ) we can distinguish, then, between the two -