“Man has risen, not fallen. He can choose to develop his capacities as the highest animal and to try to rise still farther, or he can choose otherwise. The choice is his responsibility, and his alone. There is no automatism that will carry him upward without choice or effort and there is no trend solely in the right direction. Evolution has no purpose; man must supply this for himself. The means to gaining right ends involve both organic evolution and human evolution, but human choice as to what are the right ends must be based on human evolution.”

“From horses we may learn not only about the horse itself but also about animals in general, indeed about ourselves and about life as a whole.”

“Species evolve exactly as if they were adapting as best they could to a changing world, and not at all as if they were moving toward a set goal.”

“The greatest impact of the Darwinian revolution...was that it completed the liberation from superstition and fear that began in the physical sciences a few centuries before. Man, too, is a natural phenomenon. [in "The evolutionary concept of man", 1972, p. 35.]”

“I don't think that evolution is supremely important because it is my specialty; it is my specialty because I think it is supremely important. [In: Edward J. Larson (2004) Evolution, Modern Library. p. 250]”

“Man is the result of a purposeless and natural process that did not have him in mind.”

“[Darwin] gave an answer to the tremendous question that so deeply concerns...What is Man? [He] answered this question to the effect that man is a natural product of the universe;...man is an animal, a vertebrate, a mammal, and a primate....By bringing man into the evolutionary picture, Darwin finally took the last step in our emancipation and finally made our world rational. [Yet] Darwin felt humility and awe that seem to me truly religious. ["Darwin led us into this modern world," 1959, p. 271-272.]”

“Among the things most characteristic of organisms--most distinctive of living as opposed to inorganic systems--is a sort of directedness. Their structures and activities have an adaptedness, an evident and vital usefulness to the organism. Darwin's answer and ours is to accept the common sense view...[that] the end ("telos") [is] that the individual and the species may survive. But this end is (usually) unconscious and impersonal. Naive teleology is controverted not by ignoring the obvious existence of such ends but by providing a naturalistic, materialistic explanation of the adaptive characteristics serving them. [Book review in "Science," 1959, p. 673.]”

“If a sect does officially insist that its structure of belief demands that evolution be false, then no compromise is possible. An honest and competent biology teacher can only conclude that the sect's beliefs are wrong and that its religion is a false one.”

“Man is a glorious and unique species of animal. The species originated by evolution.... Future evolution could raise man to superb heights as yet hardly glimpsed, but it will not automatically do so. As far as can now be foreseen, evolutionary degeneration is at least as likely in our future as is further progress.The only way to ensure a progressive evolutionary future for mankind is for man himself to take a hand in the process. Although much further knowledge is needed, it is unquestionably possible for man to guide his own evolution (within limits) along desirable lines. But the great weight of the most widespread...beliefs and institutions is against even attempting such guidance. ["Man's evolutionary future," 1960, p. 134.]”

“If I didn't fear I'd do you harm...I'd try to make you an atheist. I really do think that you are a deluded follower of mistaken and superstitious and cowardly theories. That's as far as I'll go....Everyone who worships a god worships a force back of all nature, no matter what they call him or it and even if they call his aspects by different names & have many "gods." If there really is such a force, then all people who worship any god or gods, worship the same god. I'd just as soon call him Ishtar or Baal or Jehovah. They're merely names for the same idea. (Letter from Simpson to Anne Roe, written ca. 1920-21, when Anne was briefly flirting with fundamentalist Christianity, American Philosophical Society archives.)”