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Single Idea 11148

[filed under theme 5. Theory of Logic / B. Logical Consequence / 3. Deductive Consequence |- ]

Full Idea

A deduction is a discourse in which, certain things having been supposed, something different from the things supposed results of necessity because these things are so.

Gist of Idea

Deduction is when we suppose one thing, and another necessarily follows

Source

Aristotle (Prior Analytics [c.328 BCE], 24b18)

Book Ref

Aristotle: 'Prior Analytics', ed/tr. Smith,Robin [Hackett 1989], p.2

A Reaction

Notice that it is modal ('suppose', rather than 'know'), that necessity is involved, which is presumably metaphysical necessity, and that there are assumptions about what would be true, and not just what follows from what.

The 15 ideas from 'Prior Analytics'

13819 Aristotle's said some Fs are G or some Fs are not G, forgetting that there might be no Fs [Bostock on Aristotle]
22271 Aristotle was the first to use schematic letters in logic [Aristotle, by Potter]
11060 Aristotelian syllogisms are three-part, subject-predicate, existentially committed, with laws of thought [Aristotle, by Hanna]
18909 Aristotelian sentences are made up by one of four 'formative' connectors [Aristotle, by Engelbretsen]
8080 Aristotelian identified 256 possible syllogisms, saying that 19 are valid [Aristotle, by Devlin]
13912 Aristotle replaced Plato's noun-verb form with unions of pairs of terms by one of four 'copulae' [Aristotle, by Engelbretsen/Sayward]
18896 Aristotle places terms at opposite ends, joined by a quantified copula [Aristotle, by Sommers]
3300 Aristotle's logic is based on the subject/predicate distinction, which leads him to substances and properties [Aristotle, by Benardete,JA]
8079 Aristotelian logic has two quantifiers of the subject ('all' and 'some') [Aristotle, by Devlin]
18911 Linguistic terms form a hierarchy, with higher terms predicable of increasing numbers of things [Aristotle, by Engelbretsen]
11149 Affirming/denying sentences are universal, particular, or indeterminate [Aristotle]
11148 Deduction is when we suppose one thing, and another necessarily follows [Aristotle]
9403 There are three different deductions for actual terms, necessary terms and possible terms [Aristotle]
14641 A deduction is necessary if the major (but not the minor) premise is also necessary [Aristotle]
8071 Aristotle listed nineteen valid syllogisms (though a few of them were wrong) [Aristotle, by Devlin]