“Nay even in the life, of the same individual there is succession and not absolute unity: a man is called the same, and yet in the short interval which elapses between youth and age, and in which every animal is said to have life and identity, he is undergoing a perpetual process of loss and reparation—hair, flesh, bones, blood, and the whole body are always changing. Which is true not only of the body, but also of the soul, whose habits, tempers, opinions, desires, pleasures, pains, fears, never remain the same in any one of us, but are always coming and going; and equally true of knowledge, and what is still more surprising to us mortals, not only do the sciences in general spring up and decay, so that in respect of them we are never the same; but each of them individually experiences a like change.”