17. The duration of man's life is but an instant; his substance is fleeting, his senses dull; the structure of his body corruptible; the soul but a vortex. We cannot reckon with fortune, or lay our account with fame. In fine, the life of the body is but a river, and the life of the soul a misty dream. Existence is a warfare, and a journey in a strange land; and the end of fame is to be forgotten. What then avails to guide us? One thing, and one alone--Philosophy. And this consists in keeping the divinity within inviolate and intact; victorious over pain and pleasure; free from temerity, free from falsehood, free from hypocrisy; independent of what others do or fail to do; submissive to hap and lot, which come from the same source as we; and, above all, with equanimity awaiting death, as nothing else than a resolution of the elements of which every being compounded. And, if in their successive interchanges no harm befall the elements, why should one suspect any in the change and dissolution of the whole? It is natural, and nothing natural can be evil. AT CARNUNTUM. END OF THE SECOND BOOK. BOOK III. 1. Man must consider, not only that each day part of his life is spent, and that less and less remains to him, but also that, even if he live longer, it is very uncertain whether his intelligence will suffice as heretofore for the understanding of his affairs, and for grasping that knowledge which aims at comprehending things human and divine. When dotage begins, breath, nourishment, fancy, impulse, and so forth will not fail him. But self-command, accurate appreciation of duty, power to scrutinize what strikes his senses, or even to decide whether he should take his departure, all powers, indeed, which demand a well-trained understanding, must be extinguished in him. Let him be up and doing then, not only because death comes nearer every day, but because understanding and intelligence often leave us before we die.