XVIII. And this also is evident, that in these natural things the wise man is not altogether inactive. He therefore, when he acts, judges that that is his duty; and because he is never deceived in forming his judgment, duty must be classed among neutral things; and this is proved also by this conclusion of reason. For since we see that there is something which we pronounce to have been rightly done (for that is duty when accomplished), there must also be something which is rightly begun: as, if to restore what has been justly deposited belongs to the class of right actions, then it must be classed among the duties to restore a deposit; and the addition of the word “justly” makes the duty to be rightly performed: but the mere fact of restoring is classed as a duty. And since it is not doubtful, that in those things which we call intermediate or neutral, some ought to be chosen and others rejected, whatever is done or said in this manner comes under the head of ordinary duty. And from this it is understood, since all men naturally love themselves, that a fool is as sure as a wise man to choose what is in accordance with nature, and to reject what is contrary to it; and so there is one duty in common both to wise men and to fools; from which it follows that duty is conversant about those things which we call neutral. But since all duties proceed from these things, it is not without reason that it is said that all our thoughts are referred to these things, and among them our departure from life, and our remaining in life. For he in whom there are many things which are in accordance with nature, his duty it is to remain in life; but as to the man in whom there either is or appears likely to be a preponderance of things contrary to nature, that man’s duty is to depart from life. From which consideration it is evident, that it is sometimes the duty of a wise man to depart from life when he is happy, and sometimes the duty of a fool to remain in life though he is miserable. For that good and that evil, as has been often said, comes afterwards. But those principal natural goods, and those which hold the second rank, and those things which are opposite to them, all come under the decision of, and are matters for the reflection of the wise man; and are, as it were, the subject matter of wisdom. Therefore the question of remaining in life, or of emigrating from it, is to be measured by all those circumstances which I have mentioned above; for death is not to be sought for by those men who are retained in life by virtue, nor by those who are destitute of virtue. But it is often the duty of a wise man to depart from life, when he is thoroughly happy, if it is in his power to do so opportunely; and that is living in a manner suitable to nature, for their maxim is, that living happily depends upon opportunity. Therefore a rule is laid down by wisdom, that if it be necessary a wise man is even to leave her herself.