 At the same time, Lewis (1946, 9–11, 254–9) also laid down a framework of assumptions, most explicitly in AKV, within which analytic epistemology flourished in the last half of the 20th century: (1) knowledge is sufficiently justified (warranted, rationally credible) true belief , (2) a belief may be justified without being true and true without being justified, and (3) epistemology seeks to elicit criteria or principles of justification or rationally credibility. 