Full Idea
If mathematical statements are don't merely report features of transient and private mental entities, it is unclear how pure intuition generates mathematical knowledge. But if they are, they express different propositions for different people and times.
Gist of Idea
If mathematics comes through intuition, that is either inexplicable, or too subjective
Source
Philip Kitcher (The Nature of Mathematical Knowledge [1984], 03.1)
Book Reference
Kitcher,Philip: 'The Nature of Mathematical Knowledge' [OUP 1984], p.50
A Reaction
This seems to be the key dilemma which makes Kitcher reject intuition as an a priori route to mathematics. We do, though, just seem to 'see' truths sometimes, and are unable to explain how we do it.