Full Idea
If we infer a cause from an effect, we must proportion the one to the other. …a body of ten ounces raised in a scale proves the counterbalance exceeds ten ounces, but not that it exceeds a hundred.
Gist of Idea
You can't infer the cause to be any greater than its effect
Source
David Hume (Enquiry Conc Human Understanding [1748], XI.105)
Book Reference
Hume,David: 'Enquiries Conc. Human Understanding, Morals', ed/tr. Selby-Bigge/Nidditch [OUP 1975], p.136