Prior to Flew, major apologies for atheism were those of Enlightenment thinkers (David Hume, Arthur Schopenhauer, Ludwig Feuerbach, and Friedrich Nietzsche).Major philosophers of Flew’s generation who were atheists: W. V. O. Quine and Gilbert Ryle. But none took the step of developing book-length arguments to support their personal beliefs.In later years, atheist philosophers who critically examined and rejected the traditional arguments for God’s existence: Paul Edwards, Wallace Matson, Kai Nielsen, Paul Kurtz, J. L. Mackie, Richard Gale, Michael Martin. But their works did not change the agenda and framework of discussion the way Flew’s innovative publications did.

Generations of Humeans have… been misled into offering analyses of causation and of natural law that have been far too weak because they had no basis for accepting the existence of either cause and effect or natural laws… Hume’s scepticism about cause and effect and his agnosticism about the external world are of course jettisoned the moment he leaves his study.