Happiness is the end of all our pursuits, an intrinsically desirable good for the sake of which we desire all other things. Aristotle seeks to give material content to this formal definition by identifying the “function,” or characteristic action, of human beings. A happy or flourishing human being is one who performs his or her function well. The characteristic action of the human being is to exercise reason; human happiness, therefore, consists in the excellent, or virtuous, activity of the rational part of the soul, in both its theoretical and practical dimensions. Intellectual virtue is acquired by birth and by teaching, whereas moral virtue is acquired as a result of habit; that is, by performing virtuous acts until these become a kind of “second nature” to us. Virtuous acts strive to realize a mean of feeling an action between the extremes of excess and defect. The standard of virtue is given not by an abstract rule but by the example of the excellent person: A virtuous act is that act that the virtuous person would do in a given set of circumstances.