“The very fact that religions are not content to stand on their own feet, but insist on crippling or warping the flexible minds of children in their favour, forms a sufficient proof that there is no truth in them. If there were any truth in religion, it would be even more acceptable to a mature mind than to an infant mind—yet no mature mind ever accepts religion unless it has been crippled in infancy. … The whole basis of religion is a symbolic emotionalism which modern knowledge has rendered meaningless & even unhealthy. Today we know that the cosmos is simply a flux of purposeless rearrangement amidst which man is a wholly negligible incident or accident. There is no reason why it should be otherwise, or why we should wish it otherwise. All the florid romancing about man's "dignity", "immortality", &c. &c. is simply egotistical delusions plus primitive ignorance. So, too, are the infantile concepts of "sin" or cosmic "right" & "wrong". Actually, organic life on our planet is simply a momentary spark of no importance or meaning whatsoever. Man matters to nobody except himself. Nor are his "noble" imaginative concepts any proof of the objective reality of the things they visualise. Psychologists understand how these concepts are built up out of fragments of experience, instinct, & misapprehension. Man is essentially a machine of a very complex sort, as La Mettrie recognised nearly 2 centuries ago. He arises through certain typical chemical & physical reactions, & his members gradually break down into their constituent parts & vanish from existence. The idea of personal "immortality" is merely the dream of a child or savage. However, there is nothing anti-ethical or anti-social in such a realistic view of things. Although meaning nothing in the cosmos as a whole, mankind obviously means a good deal to itself. Therefore it must be regulated by customs which shall ensure, for its own benefit, the full development of its various accidental potentialities. It has a fortuitous jumble of reactions, some of which it instinctively seeks to heighten & prolong, & some of which it instinctively seeks to shorten or lessen. Also, we see that certain courses of action tend to increase its radius of comprehension & degree of specialised organisation (things usually promoting the wished-for reactions, & in general removing the species from a clod-like, unorganised state), while other courses of action tend to exert an opposite effect. Now since man means nothing to the cosmos, it is plan that his only logical goal (a goal whose sole reference is to himself) is simply the achievement of a reasonable equilibrium which shall enhance his likelihood of experiencing the sort of reactions he wishes, & which shall help along his natural impulse to increase his differentiation from unorganised force & matter. This goal can be reached only through teaching individual men how best to keep out of each other's way, & how best to reconcile the various conflicting instincts which a haphazard cosmic drift has placed within the breast of the same person. Here, then, is a practical & imperative system of ethics, resting on the firmest possible foundation & being essentially that taught by Epicurus & Lucretius. It has no need of supernatualism, & indeed has nothing to do with it.”

Letter to Natalie H. Wooley (2 May 1936), in Selected Letters V, 1934-1937 edited by August Derleth and Donald Wandrei, pp. 240-241
Non-Fiction, Letters