Aristotle: Interpretation, Prior, Posterior Analytics

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Puritanboard Clerk
Good summary of how to do logic, though modern logic textbooks are far more accessible.

On Interpretation

Every proposition must contain a subject and a verb.

Contradictories: the opposite denial of an affirmation. The affirmation is of a universal character. The denial is not. One must be true and the other must be false.

Universal: that which is of such a nature that can be predicated of many subjects

Contrary: the positive/negative proposition of a universal character.

Prior Analytics

Goal: state the moods and nature of the syllogism made from possible premises.

A perfect syllogism: when the last term is contained in the middle premise as a whole, and the middle is either contained in, or excluded from, the first as in or from a whole, the extremes must be related (24a 34).

Major term: the term in which the middle is contained.

All premises in the mode of possibility are convertible to each other (32a 24). “It is not possible” = “it is impossible” = “it is necessary not to belong.”

Posterior Analytics

This is a more readable treatise than the previous one. His thesis is that not all knowledge is demonstrative. Our knowledge of immediate (i.e., not mediate) premises is independent of demonstration (72b). Logical demonstration is an inference from necessary premises.

From there Aristotle moves to some comments on essences.

Essential attribute: it belongs to its subject as an essential element (like a line in a triangle). They “inhere” in the subject. This gets tricky. When Aristotle says “inherence,” does he mean they exist “within” the subject?

With this knowledge Aristotle explores how a middle term in a syllogism, one that is necessary, leads to universal knowledge (75b).

Every syllogism is effected by means of three terms. For example, A inheres in C by means of A’s inhering in B and B’s inhering in C.

More on substance-language. Predicates which signify substance signify that the subject is identical with the predicate or a species of the predicate. For example, if A is a quality of B, then B cannot be a quality of A. You can’t have a quality of a quality.

The Heart of the Matter is the Middle Term

“Quick wit is the faculty of hitting upon the middle term instantaneously” (89b). The middle term in a syllogism can sometimes be seen as the “Cause.”
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