Emotions being called forth by imagination, their character depends on the kind of imagination which produces them. Now all impulses are directed to what is good and evil, and consist either in pursuing what appears to be a good, or in avoiding what appears to be an evil. [596] This good and this evil is sometimes a present, and sometimes a future object. Hence there result four chief classes of faulty imagination, and, corresponding with them, four classes of emotions. From an irrational opinion as to what is good there arises pleasure, when it refers to things present; desire, when it refers to things future. A faulty opinion of present evils produces care; of future evils, fear. [597] Zeno had already distinguished these four principal varieties of emotions. [598] The same division was adopted by his pupil Aristo, [599] and afterwards became quite general. Yet the vagueness, already mentioned, appears in the Stoic system in the definition of individual emotions. By some, particularly by Chrysippus, the essence of emotions is placed in the imagination which causes them; by others, in the state of mind which the imagination produces. [600] The four principal classes of emotions are again subdivided into numerous subordinate classes, in the enumeration of which the Stoic philosophers appear to have been more guided by the use of language than by psychology. [601] In treating the subject of emotions in general, far less importance was attached by the Stoics to psychological accuracy than to considerations of moral worth. That the result could not be very satisfactory, follows from what has been already stated. [602] Emotions are impulses, overstepping natural limits, upsetting the proper balance of the soul’s powers, contradicting reason—in a word, they are failures, disturbances of mental health, and, if indulged in, become chronic diseases of the soul. [603] Hence a Stoic demands their entire suppression: true virtue can only exist where this process has succeeded. As being contrary to nature and symptoms of disease, the wise man must be wholly free from them. [604] When we have once learnt to value things according to their real worth, and to discover everywhere nature’s unchanging law, nothing will induce us to yield to emotion. [605] Hence the teaching of Plato and Aristotle, requiring emotions to be regulated, but not uprooted, was attacked in the most vigorous manner by these philosophers. A moderate evil, they say, always remains an evil. What is faulty and opposed to reason, ought never to be tolerated, not even in the smallest degree. [606] On the other hand, when an emotion is regulated by and subordinated to reason, it ceases to be an emotion, the term emotion only applying to violent impulses, which are opposed to reason. [607] The statement of the Peripatetics, that certain emotions are not only admissible, but are useful and necessary, appears of course to the Stoics altogether wrong. [608] To them, only what is morally good