The Art of Logic · Part 20 · Induction and evidence · B2–C1
Induction, Analogy and Hypothesis
Part 20 of The Art of Logic: deduction moves from general truths to particular ones; induction moves from particular cases to general truths, and to the hypotheses that science tests. Verbs of evidence (suggest, indicate, show, prove, confirm, contradict), with Philo, Sophia, Marcos and Demetria.
Every syllogism we have studied begins with a general premise: all men are mortal. Tonight’s question: where do the general premises come from?
From induction: from many cases to a general truth. It is how all science begins, and it was done magnificently in this very city.
Sister Miriam Joseph distinguishes perfect induction, which examines every case (every scroll on this shelf is Greek), from imperfect induction, which examines some cases and generalises to all. Imperfect induction is never certain; its strength depends on how many cases, how varied, and whether anyone has looked for exceptions.
An argument from analogy reasons that because two things are alike in some ways, they are alike in another. It is only as strong as the likeness is relevant: the moon and the Earth are both round, so the moon has seas? (The first astronomers to see the moon through telescopes, things to come, thought so.)
A hypothesis is a proposed explanation, tested by working out what should follow if it is true, and checking. A failed prediction disproves a hypothesis; a successful one confirms it, but never proves it beyond all doubt. This is the logic of science.
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