 Most proper functions are directed toward securing things which are appropriate to nature. Thus, if I take good care of my body, then this is a proper function. The Stoics divide proper functions into those which do not depend upon circumstances and those that do. Taking care of one’s health is among the former, while mutilating oneself is among the latter (Diog. Laert., 59E). It appears that this is an attempt to work out a set of prima facie duties based upon our natures. Other things being equal, looking after one’s health is a course of action which accords with one’s nature and thus is one for which a good reason can be given. However, there are circumstances in which a better reason can be given for mutilating oneself – for instance, if this is the only way you can prevent Fagin from compelling you to steal for him.