Full Idea
It is better never to study than to be unable to distinguish the true from the false, and be obliged to accept as certain what is doubtful. One risks losing the knowledge one already has. Hence we reject all those knowledges which are only probable.
Gist of Idea
If we accept mere probabilities as true we undermine our existing knowledge
Source
René Descartes (Rules for the Direction of the Mind [1628], 02)
Book Reference
Descartes,René: 'Rules for the Direction of the Mind' [Newcomb Library 2023], p.7
A Reaction
This is usually seen nowadays (and I agree) that this is a false dichotomy. Knowledge can't be all-or-nothing. We should accept probabilities as probable, not as knowledge. Probability became a science after Descartes.