 Lewis (1946, 84–5, 93–5) drew a sharp distinction between analytic and synthetic truth. Analytic (or analytically true) statements are true by virtue of the definition of the terms they contained, and have zero intension (and universal comprehension). They are necessarily true, true in all possible worlds, no matter what else might be true of a world or thing, and yet are not equivalent in meaning to each other only due to the distinct intensions of their constituents. In MWO Lewis occasionally claimed that we create necessary truth by adopting concepts and criterial principles; in AKV he was more circumspect. It is a matter of convention or legislation that a term has the meaning it does, including sense meaning, but Lewis (1946, 155–7) denied that analytic truth was truth by convention. “A dog is an animal” is analytically true by virtue of the sense meaning of “dog” and “animal”, in particular, the inclusion of the criterion for applying the latter in the criterion for applying the former, and that isn’t a matter of convention. However, Lewis never tried to define such inclusion further. Quine (1951 [1953]) explicitly criticized Lewis and the analytic/synthetic distinction in “Two Dogmas of Empiricism”, and would have objected to the idea of resting the analytic/synthetic distinction on an undefined notion of meaning inclusion. Lewis (1946, 154), on the other hand, thought that meaning inclusion is as unproblematic and recognizable a fact as the inclusion of one plan in another, e.g. a plan to visit France in a plan to visit Paris, and didn’t need further explication. Nonetheless, taking meaning inclusion to be a primitive fact also makes it more difficult to distinguish Lewis’ analytic necessity from the rationalists’ synthetic necessity, despite his (Lewis 1946, 157) vigorous rejection of the latter. This is especially so since Lewis (1946, 129) denied that analytic truth is usefully elucidated as one that is reducible to logical truth with the substitution of definitions. For Lewis, the adequacy of a definition itself is a matter of analytic truth and what makes a truth a logical truth is that it is an analytic truth concerning certain symbols.