The chief ethical question for classical thinkers, then, is: what is the good life, the life worth living? According to Seneca:
As often as you wish to know what is to be avoided or what is to be sought, consider its relation to the Supreme Good, to the purpose of your whole life. For whatever we do ought to be in harmony with this; no man can set in order the details unless he has already set before himself the chief purpose of his life.
Ancient philosophers generally agreed in referring to this chief end as (one’s view of) eudaimonia. Aristotle, whose eudaimonistic views are perhaps the most influential of all, held that eudaimonia is synonymous with ‘doing well’ or ‘living well’, achieving the best or most excellent kind of life. It is the supreme good at which we aim in all of our action.
Now happiness (eudaimonia), more than anything else, seems complete without qualification. For we always choose it because of itself, never because of something else. Honor, pleasure, understanding and every virtue we certainly choose because of themselves, since we would choose each of them even if it had no further result; but we also choose them for the sake of happiness, supposing that through them we shall be happy. Happiness, by contrast, no one ever chooses for their sake, or for the sake of anything else at all.
Everyone, or so Aristotle thought, agrees that in fact all human beings aim at some conception of eudaimonia as the ultimate objective of all their action. Differences in ethical views, according to Aristotle, arise because of what different people understand eudaimonia actually to consist in, whether pleasure, wealth, honors, or virtue. But they do nonetheless agree that eudaimonia is our chief aim. Aristotle’s view is borne out in the history of ancient ethics, according to Julia Annas, who argues that in fact all ancient ethical theories were eudaimonistic in general structure, and that differences between them lie primarily in their divergent substantive conceptions of eudaimonia. According to Annas, moreover, the different ancient schools of thought generally agreed that the nature of eudaimonia is an objective matter, and not simply an issue of subjective feeling or preference. Human well-being is in fact grounded in the nature of things, in the proper functioning of human beings according to their nature, and is no more subjective than ‘health’ is (health is a common analogue to eudaimonia in classical thought). Reasoning along these lines, Aristotle himself concludes that true eudaimonia actually consists in living a virtuous life-to be sure, this is hardly our superficial and selfish notion of ‘happiness’. On the basis of considerations such as these it has become common in recent years for scholars to render ‘eudaimonia‘ in English not as “happiness,” but as “flourishing,” “well-being,” or “the best life.”
Ethical eudaimonism, then, is a teleological moral theory that grounds moral action in the pursuit of eudaimonia. Even if we avoid the term “happiness” and speak of “the pursuit of flourishing,” this picture of ethics may still seem quite foreign to Christian ethics, particularly as the latter has been conceived in recent centuries. But eudaimonism not only characterized classical pagan thought, but classical Christian understanding as well. According to Servais Pinckaers in his history of Christian ethics, The Sources of Christian Ethics,
To anyone with an open mind, one huge fact stands out in the history of morality: for the ancients, Christians and pagans alike, the question of happiness was primary. As they saw it, morality in its totality was simply the answer to this question. The thing was obvious; it never occurred to them to talk about it.
Let us consider, for example, the two most influential classical Christian ethicists (certainly the most influential in Lewis’s thought): St. Augustine and St. Thomas Aquinas. I will focus primarily on Augustine, since his inclusion here may seem the more surprising. In words from a sermon that today would probably cost a pastor his job were they uttered from the pulpit, Augustine grounds the motivation even for becoming a Christian in the pursuit of happiness.
All philosophers in common have sought to grasp the happy life by studying, by engaging in discussion and by living. This has been the one and only reason for philosophizing. Now I consider that philosophers are no different from us in this respect. For, if I ask you why you have believed in Christ and why you have become Christians, every man gives this true answer: “To achieve the happy life.” Therefore the appetite for the happy life is common to philosophers and Christians alike. But the question and the difference of opinion relate to where this prize, about which there is no dispute, can be found. It seems to me that it is characteristic of all men to seek the happy life, to want the happy life, to desire, long for, and pursue the happy life.