  Inasmuch as it is the distinctive function of protocol sentences to report one's evidence, a view about what sorts of contents a protocol sentence might have is in effect a view about what sorts of things can count as evidence. To abandon a view according to which the subject matter of any protocol sentence concerns the ‘private incommunicable experiences’ of some particular individual is in effect to abandon a version of the phenomenal conception of evidence. To adopt in its place a view according to which the subject matter of any protocol sentence concerns ‘public physical events’ is thus a particularly radical shift, inasmuch as this latter view seems to entail that only public physical events can count as evidence—and in particular, that experiences, formerly taken to exhaust the category of evidence, are ineligible to count as  such.[38] 