Full Idea
Sense alone does not suffice to correct visual error: we also need a degree of reason to tell us that we should believe the judgement based on touch rather than vision. Since we don't have this power in infancy, it must be attributed to the intellect.
Gist of Idea
Only judgement decides which of our senses are reliable
Source
René Descartes (Reply to Sixth Objections [1641], 439)
Book Reference
Descartes,René: 'Meditations on First Philosophy etc.', ed/tr. Cottingham,John [CUP 1986], p.65