16 But, they say, while we are moving swiftly down towards our mortal bodies, causes pursue us from the world's circles, through the working of which we become bad, ay, most wicked; burn with lust and anger, spend our life in shameful deeds, and are given over to the lust of all by the prostitution of our bodies for hire. And how can the material unite with the immaterial? Or how can that which God has made, be led by weaker causes to degrade itself through the practice of vice?
Will you lay aside your habitual arrogance, O men, who claim God as your Father, and maintain that you are immortal, just as He is? Will you inquire, examine, search what you are yourselves, whose you are, of what parentage you are supposed to be, what you do in the world, in what way you are born, how you leap to life? Will you, laying aside all partiality, consider in the silence of your thoughts that we are creatures either quite like the rest, or separated by no great difference?
For what is there to show that we do not resemble them? Or what excellence is in us, such that we scorn to be ranked as creatures? Their bodies are built up on bones, and bound closely together by sinews; and our bodies are in like manner built up on bones, and bound closely together by sinews. They inspire the air through nostrils, and in breathing expire it again; and we in like manner drew in the air, and breathed it out with frequent respirations. They have been arranged in classes, female and male; we, too, have been fashioned by our Creator into the same sexes. Their young are born from the womb, and are begotten through union of the sexes; and we are born from sexual embraces, and are brought forth and sent into life from our mothers' wombs.
They are supported by eating and drinking, and get rid of the filth which remains by the lower parts; and we are supported by eating and drinking, and that which nature refuses we deal with in the same way. Their care is to ward off death-bringing famine, and of necessity to be on the watch for food. What else is our aim in the business of life, which presses so much upon us, but to seek the means by which the danger of starvation may be avoided, and carking anxiety put away?
They are exposed to disease and hunger, and at last lose their strength by reason of age. What, then? Are we not exposed to these evils, and are we not in like manner weakened by noxious diseases, destroyed by wasting age? But if that, too, which is said in the more hidden mysteries is true, that the souls of wicked men, on leaving their human bodies, pass into cattle and other creatures, it is even more clearly shown that we are allied to them, and not separated by any great interval, since it is on the same ground that both we and they are said to be living creatures, and to act as such.
Source: Against the Heathen (New Advent)