Meditations 3.1

We ought to consider not only that our life is daily wasting away and a smaller part of it is left, but another thing also must be taken into the account, that if a man should live longer, it is quite uncertain whether the understanding will still continue sufficient for the comprehension of things, and retain the power of contemplation which strives to acquire the knowledge of the divine and the human. For if he shall begin to fall into dotage, perspiration and nutrition and imagination and appetite, and whatever else there is of the kind, will not fail; but the power of making use of ourselves, and filling up the measure of our duty, and clearly separating all appearances, and considering whether a man should now depart from life, and whatever else of the kind absolutely requires a disciplined reason,—all this is already extinguished. We must make haste, then, not only because we are daily nearer to death, but also because the conception of things and the understanding of them cease first.

Marcus Aurelius, Meditations 3.1, translated by George Long

We ought not to think only upon the fact that our life each day is waning away, what is left of it being ever less, but this also should be a subject for thought, that even if life be prolonged, yet is it uncertain whether the mind will remain equally fitted in the future for the understanding of facts and for that contemplation which strains after the knowledge of things divine and human. For if a man has entered upon his dotage, there will still be his the power of breathing, and digestion, and thought, and desire, and all such-like faculties; but the full use of himself, the accurate appreciation of the items of duty, the nice discrimination of what presents itself to the senses, and a clear judgment on the question whether it is time for him to end his own life, and all such decisions, as above all require well-trained powers of reasoning—these are already flickering out in him. It needs, then, that we should press onwards, not only because we come each moment nearer to death, but also because our insight into facts and our close touch of them is gradually ceasing even before we die.

Marcus Aurelius, Meditations 3.1, translated by C. R. Haines