DEDUCTION (de ducere, to draw from), drawing a particular truth from a general, antecedently known, as distinguished from Induction, rising from particular truths to a general. The syllogism is the form of deduction. «An enunciation in which, from the truth of certain assertions, the truth of another assertion different from the first is inferred» (Aristotle, Prior Analyt., bk. I, ch. I.).
The principle of deduction is, that things which agree with the same thing agree with one another. The principle of induction is, that in the same circumstances, and in the same substances, from the same causes the same effects will follow.
The mathematical and metaphysical sciences are founded on deduction; the physical sciences with empirical Psychology rest on induction.
Mill holds that all reasoning is ultimately inductive. For his views as to the relation of induction and deduction, the nature of the syllogism and mathematical inference, see Logic, bk. II. See also Whewell, Phil. of Induct. Sci. For the Kantian use of the term, see next article.
