  The differences in the ways these philosophers formulate their particular disjunctive characterisations may in part reflect their different particular interests in appealing to a disjunctive account of experience. For example, Snowdon’s primary concern is to block an argument about what is required for the perception of objects (see section 6.1), whereas McDowell is concerned to defend an account of experience that safeguards the distinctive epistemological role of genuine perception in providing us with propositional knowledge. It is not clear that McDowell needs to deny that there are a number of facts made perceptually manifest to you when you suffer an illusion, in which case he might allow that it is possible to group together veridical perceptions and illusions as cases in which certain facts are made manifest to their subject.