Full Idea
A priori knowledge of logic and mathematics cannot derive from meanings or concepts, because someone may possess such concepts, and yet disagree with us about them.
Gist of Idea
Meanings and concepts cannot give a priori knowledge, because they may be unacceptable
Source
Paul Horwich (Stipulation, Meaning and Apriority [2000], §12)
Book Reference
'New Essays on the A Priori', ed/tr. Boghossian,P /Peacocke,C [OUP 2000], p.169
A Reaction
A good argument. The thing to focus on is not whether such ideas are a priori, but whether they are knowledge. I think we should employ the word 'intuition' for a priori candidates for knowledge, and demand further justification for actual knowledge.