 The direct apprehension of immediately given sense presentations, and statements expressing them, are incorrigible, indubitable, not in need of verification, and not subject to error, and so, in these various (and distinct) senses, “certain”. (For a useful discussion of senses of “certainty” in Lewis, see Firth 1964 and Firth 1968 in Schilpp 1968.) However, with no possibility of error or incorrectness to contrast with the immediate awareness of the given, Lewis decides the normative label “knowledge” shouldn’t really be applied to it. Our objective interpretations of experience, on the other hand, are not only fallible—given and recalled experience doesn’t guarantee the satisfaction of our expectations about future experience--but are always subject to revision in the light of action and further experience. Past experience and our recollection of it play a key role in the credibility of these interpretations. In MWO, Lewis (1929, 337) says that memory itself is an interpretation of given present recollection, and, as such, probable knowledge with testable or verifiable implications for future experience. However, this doesn’t explain what warrants the interpretation and its expectations, a lacuna AKV corrects. Knowing for Lewis occurs in a non-instananeous “epistemological present” of sense presentation embedded in a mass of recollections or sense of past experience (Lewis 1946, 331). What is given and indubitably certain in this present are these sense presentations and these rememberings (Lewis 1946, 354, 362)), but what we recall of past experience is prima facie and non-inductively credible for us, just because so ostensibly remembered or recalled (Lewis 1946, 334), and thus can serve to make our expectations of future experience rationally credible as well. 