Pierre Gassendi (1592-1655)

French physicist and philosopher, who promoted an atomic theory of matter.
As for flesh, true, indeed, is it that man is sustained on flesh. But how many things, let me ask, does man do every day which are contrary to, or beside, his nature? So great, and so general, is the perversion of his mode of life, which has, as it were, eaten into his flesh by a sort of deadly contagion, that he appears to have put on another disposition. Hence, the whole care and concern of philosophy and moral instruction ought to consist in leading men back to the paths of Nature.
Man lives very well upon flesh, you say, but, if he thinks this food to be natural to him, why does he not use it as it is, as furnished to him by Nature? But, in fact, be shrinks in horror from seizing and rending living or even raw flesh with his teeth, and lights a fire to change its natural and proper condition . . . What is clearer than that man is not furnished for hunting, much less for eating, other animals? In one word, we seem to be admirably admonished by Cicero that man was destined for other things than for seizing and cutting the throats of other animals. If you answer, "that may be said to be an industry ordered by Nature, by which such weapons are invented," then, behold, it is by the very same artificial instrument that men make weapons for mutual slaughter. Do they this at the instigation of Nature? Can a use so noxious be called natural? Faculty is given by Nature, but it is our own fault that we make a perverse use of it.
- Letter to Van Helmont