The term social Darwinism owes its currency and its association with free markets to an unresolved tension in Richard Hofstadter's (1944) influential Social Darwinism in American Thought, 1860-1915 (SDAT). Hofstadter's New Deal sensibility condemned both free markets and the use of biological ideas in social science; he championed economic reform and a social science purged of biology. But the Progressive Era reformers Hofstadter celebrated in SDAT - men like Lester F. Ward, Edward A. Ross, Thorstein Veblen, Charles Horton Cooley, and John R. Commons - were enthusiastic biologizers who often justified economic reform on biological grounds. Because Hofstadter's reform-good-biology-bad schema does not map upon Progressive Era reform, there are two different Hofstadters in SDAT. The first Hofstadter disparaged as social Darwinism biological justification of free markets, for this was, in his view, doubly wrong. The second Hofstadter acknowledged the biological underside of what he called Darwinian collectivism: racism, eugenics and imperialism. This essay documents and explains Hofstadter's ambivalence in SDAT, including its connection with the Left's longstanding mistrust of Darwinism as apology for Malthusian political economy.