Aristotle's philosophy is based on two naturalistic principles: centrality and hierarchy. Both play a key role in his theory of happiness. Both are empirically dubious and tend to undermine personal liberty.
For Aristotle, everything in nature has a goal or purpose. Excellence of anything, therefore, refers to the fulfillment of function or purpose. What end or purpose do all humans pursue? Aristotle argues that happiness is the supreme "end" of all human action. Humans have three kinds of souls: vegetative (appetitive), animal (spirited), and human (rational). We are qualitatively superior to other species because of the presence of that "higher" rational soul. Thus we have the basis for over two thousand years of anthropocentrism. And unfortunately, Aristotle never empirically verified the existence of these three souls. They are really explanatory constructs. Today we know that these functions (along with many other functions) are performed by our brains and spinal cords. But anyway... Aristotle attributed our human nature to this "higher" rational soul. Like Plato, Aristotle argued that in the sphere of human action, the function of that "higher soul" is to control the other two "lower souls."
Aristotle was also intellectually infatuated with the "middle" or "centrality." Everything good, naturally, resides in the middle. Hence, the earth must be the center of the universe. Moral virtue, therefore lies midway between the vices of excess and deficiency. Thus the "Good Life" is one of moderation in all spheres of deliberate human action. When faced with fear, the virtue of courage is bordered by both foolhardiness and cowardice. Then, Aristotle goes on to identify many other spheres where virtue might be exercised. Virtue is also contextual. Again, doing the right thing requires you to "do it" at the right time (not too early, not too late), at the right place, and right degree (not too much, not too little.
So everything that we deliberately pursue aims at the goal of happiness. Unfortunately, not everything we pursue actually leads to happiness. We all make mistakes by going after the wrong things, at the wrong place, and/or wrong degree. (But that doesn't necessarily disprove his general hypothesis.) He argues that there are three main ways that humans pursue happiness, or the "Good Life:" a life in pursuit of pleasure (experience), a life in pursuit of honor (military), a life in pursuit of wisdom (contemplation). For now, let's focus on the pursuit of pleasure. Aristotle, distinguishes between the experience of higher and lower pleasures. Unfortunately, he wrongly believed that only humans are capable of experiencing the higher intellectual pleasures. Higher intellectual pleasures are qualitatively and quantitatively superior to lower pleasures, which are the products of our "lower" nature. Thus, if we never experience higher pleasures we are not fulfilling our higher purpose, and therefore are not really happy. Even if we believe we're happy! I suspect that Aristotle would say that the vast majority of humans do not live happy lives, even though they believe they are happy. After all, most humas are not capable of living happy lives because they lack either the natural intelligence or the moral training to be virtuous. Three final caveats: First, it is natural (and good) for "virtuous people" to rule. Second, you cannot be the judge of your own happiness. It requires third-party verification. And Third, happiness can only be predicated over a lifetime, therefore, a happy life can only be identified by third parties after you're dead. Thus young people have only the potential to be happy. But if you are 21 years old and still lack moral virtue, that potential is rather low. And, of course, it's natural (and good) for old people to rule over young people. (Right now I won't go into his idea than men ought to rule over women and animals.)
Aristotle is challenging for any libertarian. Why? There's a lot of good, old-fashioned common sense! He's obviously right in affirming that we're rational animals that live in cities. It's also probably true that a life of moderation is more likely to contribute to at least a long life. But then, most of us acknowledge that many "good lives" are posthumously valued because they have been cut short. However, libertarians are obviously concerned with his propensity to defend natural social hierarchies, which tend to concentrate power in the "upper classes." Overall, there is no necessary reason for a libertarian to reject virtue-based ethics. After all, it's your life. However, we are concerned with your political views, especially if seek to set yourself up (and/or your cronies) in that "higher" social status, and rule over the rest of us.
My next blog entry will delve deeper into the question of whether happiness requires third-party attribution by outside experts, and whether that determination must be post-mortem.