The perfect joys of heaven do not satisfy the cravings of nature.

If human nature eventually is going to take the place of nature everywhere, those of us who have been naturalists will have to transpose the faith in nature which is inherent in the profession to a faith in man-if necessary, man alone in the world.

Drive Nature from your door with a pitchfork, and she will return again and again.

The thief and the murderer follow nature just as much as the philanthropist.

Scenery is fine-but human nature is finer.

Whenever man forgets that man is an animal, the result is always to make him less humane.

Before Man made us citizens, great Nature made us men.

The essence of being human is that, in the brief moment we exist on this spinning planet, we can love some persons and some things, in spite of the fact that time and death will ultimately claim us all.

That a thing is unnatural ... is no argument for its being blamable; since the most criminal actions are, to a being like man, not more unnatural than most of the virtues.

It disturbs me no more to find men base, unjust, or selfish than to see apes mischievous, wolves savage, or the vulture ravenous for its prey.