Full Idea
If after the constant conjunction of two objects (e.g. heat and flame) we are determined by custom alone to expect the one from the appearance of the other,this explains why we can draw an inference from a thousand objects which we couldn't draw from one.
Gist of Idea
If we infer causes from repetition, this explains why we infer from a thousand objects what we couldn't infer from one
Source
David Hume (Enquiry Conc Human Understanding [1748], V.I.36)
Book Reference
Hume,David: 'Enquiries Conc. Human Understanding, Morals', ed/tr. Selby-Bigge/Nidditch [OUP 1975], p.43
A Reaction
This is Hume's best statement of the problem of the difficulty of demonstration the logic of induction.