Book 4
12
The opposite of Unity, then, is Plurality; and so the opposites of the above-mentioned concepts—Otherness, Dissimilarity, Inequality and everything else which is derived from these or from Plurality or Unity— fall under the cognizance of the aforesaid science. And one of them is Oppositeness; for this is a form of Difference, and Difference is a form of Otherness.
13
Hence since the term one is used in various senses, so too will these terms be used; yet it pertains to one science to take cognizance of them all. For terms fall under different sciences, not if they are used in various senses, but if their definitions are neither identical nor referable to a common notion.
14
And since everything is referred to that which is primary, e.g. all things which are called one are referred to the primary One, we must admit that this is also true of Identity and Otherness and the Contraries. Thus we must first distinguish all the senses in which each term is used, and then attribute them to the primary in the case of each predicate, and see how they are related to it; for some will derive their name from possessing and others from producing it, and others for similar reasons.
15
Thus clearly it pertains to one science to give an account both of these concepts and of substance (this was one of the questions raised in the DifficultiesSee Aristot. Met. 3.1.8-10, Aristot. Met. 3.2.18, 19.), and it is the function of the philosopher to be able to study all subjects.
16
If this is not so, who is it who in will investigate whether Socrates and Socrates seated are the same thing; or whether one thing has one contrary, or what the contrary is, or how many meanings it has?Cf. Aristot. Met. 10.4. and similarly with all other such questions.
17
Thus since these are the essential modifications of Unity qua Unity and of Being qua Being, and not qua numbers or lines or fire, clearly it a pertains to that sciencei.e., Philosophy or Metaphysics. to discover both the essence and the attributes of these concepts.
