The Aristotelian Ethics all aim to begin with approximate but uncontroversial starting points. In the Nicomachean Ethics Aristotle says explicitly that one must begin with what is familiar to us, and "the that" or "the fact that" (NE I.1095b2-13). Ancient commentators agree that what Aristotle means here is that his treatise must rely upon practical, everyday knowledge of virtuous actions as the starting points of his inquiry, and that he is supposing that his readers have some kind of experience-based understanding of such actions, and that they value noble and just actions to at least some degree.[11]
Elsewhere, Aristotle also seems to rely upon common conceptions of how the world works. In fact, some regard his ethical inquiries as using a method that relies upon popular opinion (his so-called "endoxic method" from the Grk. endoxa). There is some dispute, however, about exactly how such common conceptions fit into Aristotle's method in his ethical treatises,[12] particularly since he also makes use of more formal arguments, especially the so-called "function argument," which is described below.
Aristotle describes popular accounts about what kind of life would be a eudaimonic one by classifying them into three most common types: a life dedicated to pleasure; a life dedicated to fame and honor; and a life dedicated to contemplation (NE I.1095b17-19). To reach his own conclusion about the best life, however, Aristotle tries to isolate the function of humans. The argument he develops here is accordingly widely known as "the function argument," and is among the most-discussed arguments made by any ancient philosopher.[13] He argues that while humans undergo nutrition and growth, so do other living things, and while humans are capable of perception, this is shared with animals (NE I.1098b22-1098a15). Thus neither of these characteristics is particular to humans. According to Aristotle, what remains and what is distinctively human is reason. Thus he concludes that the human function is some kind of excellent exercise of the intellect. And, since Aristotle thinks that practical wisdom rules over the character excellences, exercising such excellences is one way to exercise reason and thus fulfill the human function.
One common objection to Aristotle's function argument is that it uses descriptive or factual premises to derive conclusions about what is good.[14] Such arguments are often thought to run afoul of the is-ought gap.
The highest good
In his ethical works, Aristotle describes eudaimonia as the highest human good. In Book I of the Nicomachean Ethics he goes on to identify eudaimonia as the excellent exercise of the intellect, leaving it open whether he means practical activity or intellectual activity. With respect to practical activity, in order to exercise any one of the practical excellences in the highest way, a person must possess all the others. Aristotle therefore describes several apparently different kinds of virtuous person as necessarily having all the moral virtues, excellences of character.
- Being of "great soul" (magnanimity), the virtue where someone would be truly deserving of the highest praise and have a correct attitude towards the honor this may involve. This is the first such case mentioned in the Nicomachean Ethics.[15]
- Being just in the true sense. This is the type of justice or fairness of a good ruler in a good community.[16]
- Phronesis or practical wisdom, as shown by good leaders.[17]
- The virtue of being a truly good friend.[18]
- Having the nobility kalokagathia of a gentleman.[19]
Aristotle also says, for example in NE Book VI, that such a complete virtue requires intellectual virtue, not only practical virtue, but also theoretical wisdom. Such a virtuous person, if they can come into being, will choose the best life of all, which is the philosophical life of contemplation and speculation.
Aristotle claims that a human's highest functioning must include reasoning, being good at what sets humans apart from everything else. Or, as Aristotle explains it, "The function of man is activity of soul in accordance with reason, or at least not without reason." He identifies two different ways in which the soul can engage: reasoning (both practical and theoretical) and following reasoning. A person that does this is the best because they are fulfilling their purpose or nature as found in the rational soul, similar to how the best horse in a chariot race is the fastest horse etcetera.
- (The wise person will) be more than human. A man will not live like that by virtue of his humanness, but by virtue of some divine thing within him. His activity is as superior to the activity of the other virtues as this divine thing is to his composite character. Now if mind is divine in comparison with man, the life of the mind is divine in comparison with mere human life. We should not follow popular advice and, being human, have only mortal thoughts, but should become immortal and do everything toward living the best in us. (NE 10.7)
In other words, the thinker is not only the 'best' person, but is also most like God.
