All I say is that I think it is damned unlikely that anything like a central cosmic will, a spirit world, or an eternal survival of personality exist. They are the most preposterous and unjustified of all the guesses which can be made about the universe, and I am not enough of a hair-splitter to pretend that I don't regard them as arrant and negligible moonshine. In theory I am an agnostic, but pending the appearance of radical evidence I must be classed, practically and provisionally, as an atheist.
Letter to Robert E. Howard (16 August 1932), in Selected Letters 1932-1934 edited by August Derleth and Donald Wandrei, p. 57