Two topics are discussed in this book. They are incontinence and pleasure. By incontinence is meant lack of proper self-control. It lies somewhere between the virtue of temperance and the vice of intemperance. It indicates a lesser amount of self-control than temperance but more than belongs to intemperance. Pleasure is discussed in several parts of the Nicomachean Ethics and in this particular book attention is directed to the specific ways in which pleasure may influence the course of human conduct.
The discussion concerning incontinence which occupies the greater portion of this book brings to light an important characteristic of Greek ethics and one that stands in sharp contrast with the views presented in the Judeo-Christian tradition. It has to do with the relationship between knowledge and the performance of good acts. Among the Greeks it appears to have been taken for granted that knowledge of what is good would necessarily be followed by right conduct. They believed it was only ignorance of what was really good for a person that would ever cause him to choose that which was bad. This was the view that had been proclaimed by Socrates and it occurs throughout the writings of Plato. Aristotle is in essential agreement with this view but he finds that it is necessary to place certain qualifications on the doctrine in order to bring it into harmony with the observed facts of experience. From all appearances it does seem to be true that people often do act in a manner that is contrary to that which they know they ought to do. In the Judeo-Christian tradition this is explained by saying that both man's will and his intellect have been corrupted by the Fall through which original sin was introduced into the world. There is nothing comparable to this among the Greek philosophers. They regarded reason as divine and hence the rational element in human beings was always on the side of the good. It was through the influence of the physical body that ignorance and its accompanying evil came to have a place in human life.
Apparently Plato was to some extent aware of the problem involved in making knowledge equivalent to virtue for he offers an explanation to show how it is possible for one to know something in one sense of the word and yet to act contrary to it. He uses the analogy of birds in an aviary. The keeper of the aviary owns all the birds that are kept within the enclosure but he does not have all of them in his hand at any one time. Thus it can be said of a particular bird that he both has it and that he doesn't have it. This is like the multitude of ideas which one may have in his possession but they are not all at the center of his consciousness at a particular moment. Since only those ideas of which one is fully conscious at the moment can be designated as real knowledge, it is quite possible for him to act contrary to those ideas of which he has been conscious at some other time. This seems to imply that there are degrees of knowledge and the truth of the doctrine that knowledge is virtue belongs only to the highest or at any rate to the higher degrees.
While Aristotle is somewhat critical of the way in which the doctrine has been stated by both Socrates and Plato he is in full sympathy with the main core of their teaching and he defends at some length the main premise on which it is based. The substance of his argument consists in pointing out several ways in which it may appear that one is acting contrary to his knowledge when in fact he is not doing so at all. For example, he says that a person may know something in the sense that he is in possession of the information and yet at the particular moment his mind may be occupied with something else and he pays no attention to it. This is similar to Plato's reference to the birds in the aviary. Again, Aristotle tells us that a man may know the general rules concerning good conduct but fail to see that the particular case in question is one that is covered by the rule. Furthermore, one may have knowledge of what is good but be so worked on by his passions and desires that it ceases to have a definite meaning for him.
Because pleasures and pain are so closely related to what is regarded as good and evil it is necessary to raise certain questions concerning them. We need to know whether pleasure is always good and whether pain is always evil. In case these two questions are answered in the negative we need to know under what conditions either of them contributes toward good or evil. In the first place it must be recognized that pleasure is not something that exists apart from some activity. It may accompany actions which are beneficial to the individual and to society but it may also accompany activities which are harmful. Pleasures are associated both with bodily activities and also with the processes of the mind. Pleasures are not always good since they may make that which is harmful in the long run seem attractive at the moment. Neither can we say that pleasures are necessarily bad for that which accompanies actions that are truly harmful should not be designated as true pleasures. The good life is one that finds pleasures in those activities which contribute toward the development of personality rather than in those that tend to destroy or hinder its development. Viewed in this way no pleasure can be regarded as absolutely bad in itself and pleasures which are associated with the right kind of activities make an important contribution to the values of life.