Another way is, if a man uses the very thing which is defined. But this escapes notice when ho has not used the name itself of the thing defined : for example, if ho defined the sun to be a star which appears in the day-time; for he who employs the word day employs the word sun. And it is requisite, in order that such errors may be detected, to exchange the name (6voaa) for the notion (full speech, s4-yer) : for example, that clay is the passage of the sun above the earth ; for it is manifest that he who has spoken of the passage of the sun above the earth has spoken of the sun. So that ho who has employed the word day has employed the word sun. A third way is, if that which is opposed in division is defined by that which is opposed in division ; for example, that odd is greater than even by a unit. For things of the same genus opposed in division exist by nature, and odd and even are opposed in division ; for both are differences of number. (' Top.,' vi. 4.) (60.) To know what a thing is, is the same as to know why it is. What is an eclipse 1 Privation of light from the moon through the earth intercepting (the light). What causes an eclipse ? or why is the moon eclipsed 1 Because the light fails, owing to the interposition of the earth. What is symphony I A proportion (sOsses) of numbers in sounds high or deep (dli!,, Papd). Why is the high symphonious with the deep ? Because the high and deep sounds haves proportion (shin) of numbers. (` Analyt. Post.,' ii. 2.) (SI.) We seek the cause after we know that a thing is; but some times they are manifest at the same time also; but it is not possible to know the cause before we know that the thing exists. (' Analyt. Post.; ii. S.) For it is impossible to know what a thing is when we are in ignorance whether it exists or not.
And both tho notion or expression (S6-yoi) appears to give evidence to phenomena, and phenomena to the notion. (' De Cod.,' i. 3.) (62.) The cause is the middle °acre?), and in all things this is sought.
Analyt. ii. 2.) (63.) Not only that a thing " is " ought the definition (opeoriich Shin) to show, as the most part of definitions declare, but the cause also ought to be in it, and to be clear. But the notions of the definitions are as conclusions : for example, what is quadrature ? It is a rectangular equilateral figure being equal to a figure of unequal sides." And such a definition is an expression of the conclusion. But the defi nition which says that quadrature is invention of a middle, states the cause of the.thing. (' De Animal.; ii. 2, § 1.) (64.) And it appears that not only what a thing is, is useful towards knowing the causes e7 of the accidents of essences -rah °bakes), as in mathematics what a straight lino is and what a curved lino is, or what a line and a plane are, is useful towards seeing how many right angles the angles of a triangle are equal to ; but conversely also the accidents help in a great degree to perceiving what the thing is; for when wo aro able by the appearance (seavrairta) to give an account of the accidente either of all or of the greater part, then con cerning the essence also we shall be able best to speak ; for of all demonstration what a thing is (ri et ?sea), is the beginning. So that in all definitions in which it doss not happen that we can recognise the accidents, and cannot even fonn a conjecture of them easily, it ie mani feet that they are all enunciated dialectically (Eiastrnifsc) end emptily (esvc7n). e De Animal.; i. 1, § (65.) And of some things some other thing is the cause, and of other timings not.
Accordingly it is manifest that of those also which belong to the class of what a thing " is," some are itnniediato (6,unra) and first prin ciples (apart), which; we must assume (taroOlreal) both to be, and we must assume what they are, or in some other way make clear, which the arithmetician does ; for both what unity is and that it is he assumes. But as to those things which have a middle (idros), and of which something else is the cause of the essence, we can, as we have said, show by demonstration. (`Analyt. Post.,' ii. 9.) (66.) And of proposition (putting, placing, Obrir) that which takes for granted either of the parts of the enunciation, for example, that a thing is, or is not, is Hypothesis (brothels): but the proposition with out this is Definition ; for the definition is proposition (Bean); for the arithmetician lays down (puts, places, rtOsrad that the unit is indi visible, as far as quantity is concerned : but it is not hypothesis; for what a unit is and that there is a unit is not the same thing. ('Analyt.
Post,' L 2.) (67.) All demonstrative science is about three things, two of which are assumed to be ; and these two are genus, the affections (TaOhaara) of which by themselves it contemplates, and what are called common axioms (41awara) from which first principles science demonstrates; and thirdly, the affections Orden) of which what each means it takes for granted. (' Analyt. Post.' L I0.) (68.) It is clear that it is not possible to demonstrate the peculiar first principles of each thing : for those first principles will be the first principles of all things, and knowledge of those is that which is supreme over all For he knows more who knows from the higher causes : for he knows from the prior when he knows from causes which depend not on other causes. So that if he knows more and most, that science also will be both more and most. (' Analyt. Post.' i. 9.) (69.) Accordingly that it is impossible to have science from demon stration, if a man does not know the first principles which admit of no middle (lyxal al d,ufaat), has been said before. But as to the know ledge of things which want a middle, a man may be in doubt. All animals have an innate discerning faculty, which men call perception (afoOnaty). And as they have perception, in some animals there is a permanence (par6) of the thing perceived (caoinaa); and in others there is not. In those animals, then, in which it is not, there is either wholly, or with respect to things of which there is no permanence in them, no knowledge except of what they perceive : but in those ani mals in which there is, there is the faculty of having the perception in the mind, though they do not then perceive. And many animals being such, there results a difference among them, so that some have reason owing to the permanence of such things, and some have not. Accordingly from perception comes memory (jarksa), as we call it, and from the frequent remembrance of the same thing comes experience (1,uviipla): for many remembrances in number are one experience. And from experience, or from a whole thing remaining tranquil in the mind as one thing apart from the many, whatever thing in all these things is as one and the same thing, is the beginning of art and of science; if about production (7isecris), of art; if about that which is or being (rb dr), of science. Neither indeed do the faculties (Ffeir) exist in the mind separate, nor do they proceed from other faculties which are more intelligent, but they proceed from perception ; as In battle when a flight has taken place, when one stops, another stops, and then another, until order igrestored : and the mind exists in such a manner as to have the faculty of being so affected. For when one thing of things which are not different stands, it first of all is in the mind as universal (for the mind perceives the individual, but the per ception belongs to the universal, for example, it belongs to mankind, but not to a man (' Callias ') ): and again it abides in these until the undivided and the universal have abided : for example, such or such an animal abides, until animal generally abides ; and in this in like manner. It is manifest then that it is necessary for us to know the first things by induction : for perception also in this manner produces the universal in the mind.
And since of the faculties that concern the understanding (adroga), by which we learn the truth, some are always true, and some admit of falsehood, as opinion and reasoning (Ahoy/hos) ; and since science and intellect (hrta-rhini Ka2 voih) are always true, and there is no other kind of science more exact than intellect, and since the first principles are clearer than the demonstrations, and since all science is together with reason (thyas),* there can be no science of the first principles : and since nothing can be truer than science except intellect, intellect must be intellect of first principles : and this appears both from considering these things, and that the beginning of demonstration is not demon stration, so that neither is science the beginning of science. If then we have no kind of truth which exists independent of science, intellect (vein) must be the beginning of science. C Analyt. Poet.' ii. 19.)