Having indicated the general character of the study of ethics Aristotle proceeds in Book II to a more detailed account of the virtues that are included in the moral life. Certain observations are made concerning the nature of virtue and its relation to the various activities which make up the life of the ordinary human being. Unlike those moralists who describe the good life in terms of obedience to a set of laws which are imposed on people from without, Aristotle sets forth the view that the good life consists in the proper development and control of those elements that are within one's own nature. It is for this reason that he is often referred to as an exponent of self-realization ethics. The essential meaning of this doctrine is that the self to be realized or the one which is the standard of goodness consists of an organization of the elements that are included in one's entire personality. The principle to be used in bringing about this organization is that the larger and more inclusive interests should always be given preference over the smaller and less inclusive ones. This means, for example, that the appetites and desires which are for the moment or which will endure for only a short period of time should always be subordinated to those which pertain to life as a whole. Or, again, the possession of material goods which have a positive value for human life must not be allowed to interfere with the achievement of spiritual values. To permit them to do so would be to sacrifice a more inclusive good for the sake of a smaller one. The same principle must be used in adjusting one's own interests to the welfare of others. It is always a mistake to sacrifice the welfare of a large group in order to promote the interests of a smaller one. When the elements included in it are properly organized human nature is good. It is the perversion of it that constitutes moral evil.
As mentioned before, it is impossible in the field of ethics to lay down exact rules of conduct that will be entirely adequate for every new situation which arises. While it is true that all human beings are alike in some respects, there are individual differences. Then, too, the circumstances under which people live are constantly changing and what is appropriate for one person in a specific situation will not be what another person should do under different conditions. Even so, it is possible to indicate some general principles that will serve as a guide for anyone who wishes to use them regardless of the circumstances under which he is living. One of these principles has to do with the acquisition of virtues. People are not born with a set of virtues embedded in their nature. Neither are they born with a nature which is inherently evil. The fact is that human nature has possibilities both for good and for evil. It is up to the individual to determine which ones shall be realized. It is the purpose of the study of ethics to guide one toward the realization of his best possibilities. This involves the acquisition of virtues and this is brought about through the development of habits. As Aristotle sees it, the good person is one who finds pleasure and satisfaction in doing those things that are in harmony with his own good and also the good of others. This is not something that happens to a person all at once. It is acquired through actions which are carried out over a considerable period of time. The formation of good habits is often a difficult task especially during the earlier stages of the process. At first the actions are carried out from a sense of duty but the longer they are continued the easier they become and once the habit has been developed the activity requires very little effort. In fact, it has a tendency to become automatic. Now a good character consists of a good set of habits and it is not until these have been formed that one can rightly be called a good person. While the habits are being formed he is making progress toward the good life but he has not fully arrived until they have become apart of his nature.
With reference to the appetites and desires which are closely associated with the physical body the virtuous life consists in following the doctrine of the "golden mean." According to this principle an activity is good only insofar as it is present in the right amount. Too much or too little is an evil to be avoided but "the right amount for the right person, in the right place, and at the right time" is a positive good. This view stands in sharp contrast with the one that classifies all activities as being entirely good or entirely bad. That which is harmful when carried to an excess may be a positive good so long as it is kept within proper bounds. Each person must determine for himself just what is the proper amount in his particular situation. This sounds like a dangerous procedure which would permit each individual to judge the appropriate amount of any activity on the basis of his wishes or desires. But this is not what Aristotle meant. He insisted that the decision should be based not on one's feelings but on what reason tells him is most appropriate with reference to his life as a whole. In those instances where his judgment is likely to be influenced by his immediate desires he should make proper allowances for this fact and thus make it possible for reason to fulfill its task. Again, attention is called to the fact that the doctrine of the golden mean does not permit a certain amount of any kind of activity which may appear attractive at the moment. There are some things such as injustice, wanton cruelty, and the like which make no contribution to the proper development of human personality. They are always injurious in any amount and for this reason they should not be tolerated at all.