 With respect to the first step, Lewis (1946) in AKV will deny Quine’s assumption that objective statements never entail conditionals about experience without supposing other objective statements true and his assumption that the antecedents of these conditionals are never themselves certain, as we shall see in the next two sections. Moreover, objective hypotheses, despite their various interconnections in a system of empirical belief, aren’t tested as a “block”, but have separable and distinct probabilistic connections to others (but not thereby to all) and to experience establishing differing antecedent probabilities and degrees of confidence, in the light of which the relevance of tests for the probability of the various hypotheses needs to be assessed differentially. (Lewis, 1936b, reprinted in Lewis 1970, 285–6, Lewis 1946, 349–52). However, even so, there may be room for alternative ways of modifying systems of hypotheses and their degrees of credibility in the light of experience, and different responses to probabilities that are unsettled and may change with future testing. So, in an unpublished lecture, Lewis (1936b, 282–7) says we are left with pragmatic factors like economy, convenience, simplicity, or making the least alteration to beliefs, at least for the time being, to choose “working hypotheses” even if they don’t count as empirical knowledge. Lewis (1946) omits this discussion from AKV. Nonetheless it highlights the need for Lewis to provide a positive account of non-empirical, non-inductive a priori knowledge of principles explicating our concepts and how we have it, not just a negative account that simply contrasts it with empirical knowledge. 