Full Idea
Before Descartes, one could not be impure, immoral, and know the truth. After Descartes, direct evidence is enough, and we have a nonascetic subject of knowledge; this change makes possible the institutionalisation of modern science.
Clarification
'Nonascetic' means self-discipline is not required
Gist of Idea
Modern science comes from Descartes' view that knowledge doesn't need moral purity
Source
report of René Descartes (Meditations [1641]) by Michel Foucault - On the Genealogy of Ethics
Book Reference
Foucault,Michel: 'Essential Works 1954-1984 I: Ethics', ed/tr. Rabinow,Paul [Penguin 1994], p.279
A Reaction
I would have thought Gassendi and the British Empiricists would be a more plausible source for this shift of attitude. Plato would relegate modern science to a lower level of knowledge.