A Greek word literally translated as "living well" or "doing well", eudaimonia (ευδαιμονια) is an originally Aristotelian concept dealing with happiness and its purpose in human life.

Dealt with extensively in Aristotle's work Nicomachean Ethics, Aristotle's account of happiness is connected to his work with the nature of the soul. What distinguishes living things from inanimate objects in Aristotle's view is their capacity to do specific things. From De Anima:

"The parts of plants are also organs,1 though altogether simple ones; the leaf, for instance, is a shelter for the shell, and the shell for the fruit, and similarly the roots correspond to a mouth, since both draw in food." 2

Here, Aristotle outlines his conception of function as central to understanding the soul of a living thing. All of the parts of an organism, as in this analogy with the plant, share a common function. All living things share the characteristic of possessing organs which act together to further its own existence. All capacities in a living thing exist in order to accomplish some action, and that organism exhibits virtue insofar as it fulfills those capacities for action by acting in accordance with its nature.

In terms of human beings, the capacity that distinguishes them from other organisms is that of reason, or advanced thought. Again, from De Anima:

"besides these parts ... others - human beings for instance ... also have the thinking part and understanding ... For perishable things that have reasoning also have all the other parts of the soul; but not all of those that have each of the other parts also have reasoning ... " 3

Since human beings possess this advanced capacity, it is necessary that they act to fulfill it throughout their lives in order to be completely virtuous. Otherwise, they are not living according to their fullest potential and are therefore not completely human. The concept of virtue as being related to this capacity is explored in greater depth in the Nicomachean Ethics:

"We have found, then, that the human function is the soul's activity that expresses reason or requires reason ... the same is true without qualification in every case, when we add to the function the superior achievement that expresses the virtue ... now we take the human function to be a certain kind of life, and take this life to be the soul's activity and actions that express reason ... the excellent man's function is to do this finely and well ... each function is completed well when its completion well when its completion expresses the proper virtue. Therefore, the human good turns out to be the soul's activity that expresses virtue." 4

Virtue can then be understood as that life of action which expresses the human function for advanced thought. Happiness can be understood in a similar manner. It is that complete end which is pursued for itself; it is that state which follows from understanding the importance of the virtuous life. By knowing why such a life is the only one proper for a human being, a person becomes happy, experiencing eudaimonia as a result of knowing that they are fulfilling their true function.

1 gk. organon : Also translated as "tool".
2 Aristotle. De Anima. tr. Terence Irwin & Gail Fine. 412 b.
3 p. 415 a.
4 Aristotle. Nicomachean Ethics. tr. Terence Irwin & Gail Fine. 1098 a.