So powerful did Finneyism become that it virtually replaced classical Protestant theology with modern “Decisionism.” Let us examine how “Decisionism” overtook the churches and produced today's apostasy. In his book, Revival and Revivalism: The Making and Marring of American Evangelicalism 1750-1858, Iain H. Murray points out that evangelicalism turned away from the old idea of conversion in the nineteenth century to the “Decisionism” taught by Charles G. Finney (1792-1875).