The negative assumption is that supernatural religion is erroneous, and that this error has important consequences. The positive assumption is the belief in free discussion, the devaluation of any claim to authority except that of the scholar or scientist, a belief in morality as a guide to behaviour, and in the power of men to shape their world and determine their futures. The common assertion that humanists view man as basically good is mistaken; it would be more accurate to say that they see him as powerful. They attribute his malice and aggression to his social and biological circumstances, and accordingly demand that he try to assume responsibility for himself and his society. [...] The attack on religion is that by diverting men's energies and attention to their fate in a future life, it hinders the realization of such happiness as they can achieve on earth.
-- Varieties of Unbelief, p. 8-9 (Heinemann, 1977)