Full Idea
Abstract reasonings are employed, either to assist experience in the discovery of natural laws, or to determine their influence in particular instances, where it depends upon any precise degree of distance or quantity.
Gist of Idea
Reason assists experience in discovering laws, and in measuring their application
Source
David Hume (Enquiry Conc Human Understanding [1748], IV.I.27)
Book Reference
Hume,David: 'Enquiries Conc. Human Understanding, Morals', ed/tr. Selby-Bigge/Nidditch [OUP 1975], p.31