He who has cast seed into the womb departs; another cause takes and works upon it and completes the child. How wonderful the result from such a beginning! The child, again, takes food down its throat; another cause takes and transforms it into sensation, motion, in a word into life and strength and other things, how many and surprising! Consider then these things happening in such hidden ways, and view the power which produces them just as we perceive the gravitation and levitation of bodies; not indeed with our eyes, yet none the less clearly.