Full Idea
When we follow long mathematical proofs we lose our a priori warrants for their beginnings.
Gist of Idea
In long mathematical proofs we can't remember the original a priori basis
Source
Philip Kitcher (The Nature of Mathematical Knowledge [1984], 02.2)
Book Reference
Kitcher,Philip: 'The Nature of Mathematical Knowledge' [OUP 1984], p.45
A Reaction
Kitcher says Descartes complains about this problem several times in his 'Regulae'. The problem runs even deeper into all reasoning, if you become sceptical about memory. You have to remember step 1 when you do step 2.