Return to Aristotle, Prior Analytics
In the first place it is requisite to say what the subject is of the present treatise, and for the sake of what it is undertaken; viz. that it is concerning demonstration, and for the sake of demonstrative science. Afterwards, it is requisite to define what a proposition is, what a term, and what a syllogism; and also what kind of a syllogism is perfect, and what kind is imperfect. In the next place it must be shown, what it is for a thing to be or not to be in a certain whole, and what we say it is to be predicated of every thing or of nothing, of a certain multitude. A proposition, therefore, is a sentence affirming or denying something of something. And this is universal, in a part, or indefinite. But I denominate universal the being present with every thing or with nothing; in a part, the being present with something, or not with something, or not with every thing; and the indefinite, the being present, or not being present without the universal or particular; such, for instance, as that there is the same science of contraries, or that pleasure is not good. But a demonstrative differs from a dialectic proposition in this; that the demonstrative proposition is an assumption of one part of contradiction; (for he who demonstrates does not interrogate, but assumes) but the dialectic is an interrogation of contradiction. So far, however, as pertains to the framing a syllogism from either proposition, the one in no respect differs from the other. For he who demonstrates, and he who interrogates syllogize, assuming that something is present with, or is not present with something. Hence, a syllogistic proposition, indeed, will be simply an affirmation or negation of something concerning something, after the manner above-mentioned. But a proposition is demonstrative, if it is true, and is assumed through hypotheses from the beginning. And a dialectic proposition, with respect to him who enquires, is an interrogation of contradiction; but with respect to him who syllogizes, is an assumption of that which is seen and probable, as we have observed in the Topics. What, therefore, a proposition is, and in what the syllogistic, demonstrative, and dialectic proposition differ from each other, will be accurately shown in the following treatises; but for the present purpose, what has been now determined by us may suffice. But I call that a term into which a proposition is dissolved; as, for instance, that which is predicated, and that of which it is predicated, whether to be or not to be is added or separated. And a syllogism is a discourse, in which certain things being admitted, something else different from the things admitted necessarily happens, in consequence of the existence of these admitted propositions. I say, that in consequence of these admitted propositions, something else happens. And when I say that something else happens through these, I mean that there is no need of any external term, in order to the existence of the necessary consequence. Hence I call that a perfect syllogism, which requires nothing else besides the things assumed in order that the necessary consequence may be apparent. But I denominate that an imperfect syllogism, which requires one or more things, which through the supposed terms are necessary, and yet are not assumed through propositions. And it is the same thing, for one thing to be in the whole of another, and for one thing to be predicated of the whole of another, when nothing can be assumed of the subject, of which the other may not be asserted: and to be predicated of nothing is assumed after a similar manner.
Return to Aristotle, Prior Analytics
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