Full Idea
Every attribution of apriority to a proposition is tacitly an attribution of a cognitive ability to some thinker.
Gist of Idea
Attributing apriority to a proposition is attributing a cognitive ability to someone
Source
Roy Sorensen (Vagueness and Contradiction [2001], 6.3)
Book Reference
Sorensen,Roy: 'Vagueness and Contradiction' [OUP 2004], p.100
A Reaction
The ability would include a range of background knowledge, as well as a sheer power of intellect. If you know all of Euclid's theorems, you will spot facts about geometrical figues quicker than me. His point is important.