Full Idea
Archimedes sought but one firm and immovable point in order to move the entire earth. Just so, great things are to be hoped for if I succeed in finding just one thing, however slight, that is certain and unshaken.
Gist of Idea
Only one certainty is needed for progress (like a lever's fulcrum)
Source
René Descartes (Meditations [1641], §2.24)
Book Reference
Descartes,René: 'Discourse on Method/The Meditations', ed/tr. Sutcliffe,F.E. [Penguin 1968], p.102
A Reaction
The classic foundationalist difficulty is that you may find something totally certain, but is it a fulcrum? Or is it just minimal, boring and useless?