Full Idea
The primary bearer of apriority is the propositional attitude (believing, knowing, guessing and so on) rather than the proposition itself. A proposition could be a priori to homo sapiens but a posteriori to Neandethals.
Gist of Idea
It is propositional attitudes which can be a priori, not the propositions themselves
Source
Roy Sorensen (Vagueness and Contradiction [2001], 6.3)
Book Reference
Sorensen,Roy: 'Vagueness and Contradiction' [OUP 2004], p.99
A Reaction
A putative supreme being is quite useful here, who might even see the necessity of Arsenal beating Manchester United next Saturday. Unlike infants, adults know a priori that square pegs won't fit round holes.