Reasoning from the analogy of "right" physical acts, he pronounces that rightness always means adaptation or adjustment to the special requirements of a situation. To this adjustment he gives a quantitative interpretation. To do (or to feel) what is right in a given situation is to do or to feel just the amount required—neither more nor less: to do wrong is to do or to feel too much or too little—to fall short of or over-shoot, "a mean" determined by the situation. The repetition of acts which lie in the mean is the cause of the formation of each and every "goodness of character," and for this "rules" can be given.
(2) What then is a "moral virtue," the result of such a process duly directed? It is no mere mood of feeling, no mere liability to emotion, no mere natural aptitude or endowment, it is a permanent state of the agent's self, or, as we might in modern phrase put it, of his will, it consists in a steady self-imposed obedience to a rule of action in certain situations which frequently recur in human life. The rule prescribes the control and regulation within limits of the agent's natural impulses to act and feel thus and thus. The situations fall into groups which constitute the "fields" of the several "moral virtues", for each there is a rule, conformity to which secures rightness in the individual acts. Thus the moral ideal appears as a code of rules, accepted by the agent, but as yet to him without rational justification and without system or unity. But the rules prescribe no mechanical uniformity: each within its limits permits variety, and the exactly right amount adopted to the requirements of the individual situation (and every actual situation is individual) must be determined by the intuition of the moment. There is no attempt to reduce the rich possibilities of right action to a single monotonous type. On the contrary, there are acknowledged to be many forms of moral virtue, and there is a long list of them, with their correlative vices enumerated.
The Doctrine of the Mean here takes a form in which it has impressed subsequent thinkers, but which has less importance than is usually ascribed to it. In the "Table of the Virtues and Vices," each of the virtues is flanked by two opposite vices, which are respectively the excess
