in "man, economy, and state" (1962), murray rothbard argues that the liquidity preference theory of interest suffers from a fallacy of mutual determination. keynes alleges that the rate of interest is determined by liquidity preference. in practice, however, keynes treats the rate of interest as "determining" liquidity preference. rothbard states "the keynesians therefore treat the rate of interest, not as they believe they do—as determined by liquidity preference—but rather as some sort of mysterious and unexplained force imposing itself on the other elements of the economic system."