Frank Straus Meyer (/ˈmaɪ.ər/; May 9, 1909 – April 1, 1972) was an American philosopher and political activist best known for his theory of "fusionism" – a political philosophy that unites elements of libertarianism and traditionalism into a philosophical synthesis which is posited as the definition of modern American conservatism. Meyer's philosophy was presented in two books, primarily In Defense of Freedom: A Conservative Credo (1962) and also in a collection of his essays, The Conservative Mainstream (1969). Fusionism has been summed up by E. J. Dionne, Jr. as "utilizing libertarian means in a conservative society for traditionalist ends."