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Full Idea
A first principle is that similar effects proceed from the same or similar causes; that we ought to admit of no other causes …but such as are sufficient to account for the effects.
Gist of Idea
Similar effects come from similar causes, and causes are only what are sufficient for the effects
Source
Thomas Reid (Essays on Intellectual Powers 1: Preliminary [1785], 2)
Book Ref
Reid,Thomas: 'Inquiry and Essays', ed/tr. Beanblossom /K.Lehrer [Hackett 1983], p.151
A Reaction
He treats these as a priori axioms of natural philosophy. In evolution similar causes seem to produce startlingly divergent effects, such as the mating needs of male birds.