Book X · Chapter 26

A man deposits seed in a womb and goes away, and then another cause takes it and labors on it, and makes a child. What a thing from such a material! Again, the child passes food down through the throat, and then another cause takes it and makes perception and motion, and in fine, life and strength and other things; how many and how strange! Observe then the things which are produced in such a hidden way, and see the power, just as we see the power which carries things downwards and upwards, not with the eyes, but still no less plainly (vii. 85).