  Partly in response to such worries, John Locke emphasized the notion of a tacit agreement. A tacit agreement obtains if there has been no explicit agreement but matters are otherwise as if an explicit agreement occurred. A principal challenge here is explaining the precise respects in which matters are just as if an explicit agreement occurred. Moreover, many philosophers argue that appeal even to “as if” agreements cannot explain linguistic meaning. What language would participants in such an agreement employ when conducting their deliberations? Bertrand Russell observes that “[w]e can hardly suppose a parliament of hitherto speechless elders meeting together and agreeing to call a cow a cow and a wolf a wolf” (1921, p. 190). As W. V. Quine asks, then, “What is convention when there can be no thought of convening?” (1969, p. xi). Some philosophers take this argument to show that language does not rest upon convention. Others, such as Lewis, take it as impetus to develop a theory of convention that invokes neither explicit nor tacit agreement.