 The received view has it that mathematical proofs yield a priori knowledge. Yet when we rely on a computer to generate part of a proof, we appear to rely on the proper functioning of computer hardware and on the correctness of a computer program. These appear to be empirical factors. Thus one is tempted to conclude that computer proofs yield quasi-empirical knowledge (Tymoczko 1979). In other words, through the advent of computer proofs the notion of proof has lost its purely a priori character. Burge, in contrast, held the view that because the empirical factors on which we rely when we accept computer proofs do not appear as premises in the argument, computer proofs can yield a priori knowledge after all (Burge 1998). (Burge later retracted this claim: see (Burge 2013, p.31).)