Full Idea
When we have pushed up definitions to the most simple ideas and still find some ambiguity and obscurity, how can we render them altogether precise and determinate? Produce the impressions or original sentiments from which the ideas were copied.
Gist of Idea
When definitions are pushed to the limit, only experience can make them precise
Source
David Hume (Enquiry Conc Human Understanding [1748], VII.I.49)
Book Reference
Hume,David: 'Enquiries Conc. Human Understanding, Morals', ed/tr. Selby-Bigge/Nidditch [OUP 1975], p.62