Everyone has a purpose. It is irrelevant to our current discussion whether that purpose is something transcendent or objective, or whether it is subjective and relative to the individual. We have purpose -- we apply means to achieve ends; our conscious actions are goal oriented.
And, in the vein of Aristotle, we must recognize there are things which are good, and things which are maximally good. That which is good is something which is to be valued in itself. Knowledge could be an example of one such good. It is valuable to have in itself, even if it is not used. Thousands of families visit museums every summer to learn about, say, the movements of the stars, though it is difficult to conceive of how most of those will employ that knowledge in daily life. Therefore, we can say that knowledge is good to have, but perhaps is not maximally good.
Knowledge can be employed to serve other ends, as well as being an end in itself. For this reason we can say that it is not the final good. What Aristotle points out to us, though, is that all things find themselves to be extrinsically valuable, save one. The singular good, which is valuable for itself and not for anything else, is the concept of happiness.
Every action is undertaken in order, ultimately, to further one's happiness. Individuals seek to render their future selves happier by actions they undertake in the present. When ever a person expresses a choice in terms of action, he or she is attempting by implication to improve his or her circumstances, or to prevent some harm from manifesting itself. In other words, happiness is the maximally valuable thing, because all action is undertaken to make the actor happier or to prevent the actor from becoming unhappy.
Where I (and, I suspect, most) would diverge from Aristotle, however, is in the concept of happiness. Happiness is an inherently subjective concept. Those things which cause one to become content or joyous will be different for another. Happiness is a deeply personal affair. We run up against a significant epistemological problem when we attempt to define happiness: our definition will be one which satisfies us, but we cannot determine that it will satisfy others.
Even if we agree with Aristotle that all happiness is fundamentally the same, and that it can be objectively defined, we run up against the same problem of subjectivity with respect to our means. To achieve the same ultimate object of happiness, people invariably employ different means. This is evidenced by the fact that, in cases in which a group agrees upon a single goal, its members often fail to come to consensus regarding a method of proceeding to fulfill that goal.
Thus, we see happiness is valuable, and that it is subjective in its nature.
This raises a critical point. There is an idea, held by most people, that societies should be governed in a manner to make the most people happy. Such an idea is flawed, for the very simple reason that no one person or group can even know what makes another individual happy. To establish a system of laws with the goal of causing members of a society to flourish, or to live a good life, is a fallacy. Such an action assumes that we can know what will cause flourishing. But that, as we've seen, is different for each unique person.
Freedom matters. Freedom is not a maximally final good -- it matters because the good, happiness, can only be maintained when people have freedom. One cannot "introspect" into the hearts of others. If we truly value the good, then we must leave ourselves free to pursue it. Everyone has a purpose. To arrange our civilizations in an attempt to cultivate a given outcome is to undermine, ultimately, the happiness, the flourishing, of the members of our civilizations.
