Full Idea
Perception is a causal process that inputs beliefs into our doxastic system without their being inferred from or justified on the basis of other beliefs we already have.
Clarification
'Doxa' is Greek for belief
Gist of Idea
Perception causes beliefs in us, without inference or justification
Source
J Pollock / J Cruz (Contemporary theories of Knowledge (2nd) [1999], §3.2.3)
Book Reference
Pollock,J.L./Cruz,J: 'Contemporary Theories of Knowledge (2nd)' [Rowman and Littlefield 1999], p.74
A Reaction
This topic is much discussed (e.g. by MacDowell). I don't see how something is going to qualify as a 'belief' if it doesn't involve concepts and propositions. The point that we are caused to have many of our beliefs (rather than judging) seems right.