 Chisholm (1948) raised an important challenge to Lewis’ claim that a physical object statement \(P\) entails a set of counterfactual statements expressing claims about what experiences one would have or would be likely to have were one to (seem to) carry out certain tests upon being presented with certain sensory cues. If \(P\) entails \(T\), then for any \(Q\) consistent with \(P, P\) and \(Q\) also entail \(T\). However, Chisholm argued, for any material object statement \(P\) and for any sensory conditional \((S \amp A) \rightarrow  (h)E\), there will be some other material object statement \(M\) about the circumstances of perception that is consistent with \(P\), such that \(P\) and \(M\) can both be true while \((S \amp A) \rightarrow  (h)E\) is false. For example, suppose \(P\) is “There is a doorknob before one” and \((S \amp A) \rightarrow(h)E\) is “If one were to seem to see a doorknob and have the experience of reaching out with one’s hand, then, in all likelihood, one would seem to feel something hard and round”, and \(M\) is “One’s fingertips have been permanently anaesthetized”. (Expanding the understanding of \(S\) to include sensory correlates of circumstances of perception, as Lewis (1946, 245–6) suggests, presumably just requires expanding the understanding of \(M\) with some imagination.) A material object statement like \(P\), therefore, doesn’t entail sensory conditionals like \((S \amp A) \rightarrow(h)E\) . Instead of Lewis’ empiricism about the meaning and justification of material object statements, Chisholm proposed that our spontaneous perceptual beliefs about the world, e.g. that one is seeing a doorknob, are prima facie justified just by virtue of being such spontaneous perceptual beliefs, quite apart from any inductive justification from present and past experience that might be reconstructed. Lewis’ own defence of the prima facie credibility of memory, Chisholm thought, prepared the way for his alternative. Quine (1969), on the other hand, thought that Chisholm’s problem just shows that what have consequences for experience and are tested by experience are never individual material object statements in isolation from each other but only sets of them or theories. Quine saved empiricism by drawing a holistic moral from the sort of problem Chisholm posed. 