“These virtues are formed in man by his doing the actions ... The good of man is a working of the soul in the way of excellence in a complete life.”
― Aristotle, The Nicomachean Ethics
This is Aristotle's classic guide to ethics including the golden mean, the nature of friendship and other topics. While it is more a set of lecture notes than a polished philosophical treatise it still demonstrates the power of the mind of the man behind it.
In the first part he focuses on defining the nature of the highest good for human beings. That is the good at which all things aim (1094a3). This highest good is "happiness" by which is meant both "living well" and "doing well" (1095a18); that, more specifically, happiness is "an activity of the soul [which] consists in action performed in conjunction with the rational element" (1098a13), "in conformity with excellence or virtue" (1098a15), "in a complete life" 91098a16).
As he does for other subjects Aristotle approaches ethics in an organized and scientific manner with an initial emphasis on definitions such as: what is the good, virtue, justice and moral excellence? He does this with an expectation of only that level of precision that is appropriate for the subject at hand. Over the course of the middle section of the treatise the reader is introduced to the concept of the 'golden mean' by which virtues are discussed with regard to extremes (eg. courage vs. rashness) which allow for a middle ground or mean between the extremes. In book seven he discusses moral strength and weakness, and he follows this in book eight with an analysis of the nature and importance of friendship and the need for it. He makes the case that:
"The perfect form of friendship is that between good men who are alike in excellence or virtue. For these friends wish alike for one an other's good because they are good men, and the are good per se, (that is, their goodness is something intrinsic, not incidental). Those who wish for their friends' good for their friends' sake are friends in the truest sense since their attitude is determined by what their friends are and not by incidental considerations."(1156b, 6-12)
The ethics culminates in a argument for the supreme importance of contemplation. He says,
"But a wise man is able to study even by himself, and the wiser he is the more is he able to do it. . . study (contemplation) seems to be the only activity which is loved for its own sake."(1177a, 33- 1177b, 1)
The ethical principles, the method of demonstration and the sheer power of the ideas presented here make this a valuable guide even as we approach the twenty-first century.