Aristotle's Nicomachean Ethics is an analysis of character and intelligence as they relate to happiness. Here, Aristotle distinguished two kinds of "virtue," or human excellence: moral and intellectual. Moral virtue is an expression of character, formed by habits reflecting repeated choices. It is a mean between two less desirable extremes. Courage, for example, is a mean between cowardice and thoughtless rashness. Intellectual virtues are not subject to this doctrine of the mean. Nevertheless, it seemed Aristotle argued for an elitist ethics: where what"s good or virtuous can be realized only by the mature male adult of the upper class, not by women, or children, or barbarians. It was noted in class that these may have been (non-Greeks), or salaried "mechanics" (manual workers). In politics, many forms of human association can obviously be found. Aristotle did not regard politics as a study of ideal states in some abstract form, but rather as an examination of the way in which ideals, laws, customs, and property interrelate in actual cases. He thus approved the contemporary institution of slavery but tempered his acceptance by insisting that masters should not abuse their authority, since the interests of master and slave are the same. It seemed to Aristotle that the individual's freedom of choice made an absolutely accurate analysis of human affairs impossible. "Practical science," then, such as politics or ethics, was called science only by courtesy and analogy. The inherent limitations on practical science are made clear in Aristotle's concepts of human nature and self-realization. Human nature certainly involves, for everyone, a capacity for forming habits; but the habits that a particular individual forms depend on that individual's culture and repeated personal choices. All human beings want "happiness," an active, engaged realization of their innate capacities, but this goal can be achieved in a multiplicity of ways.