This chapter argues that the cosmological doctors arose as the result of a much wider realignment in Classical Greek medicine. As some doctors grew increasingly concerned about the many variables that can change from one case to the next, they rejected older forms of diagnostic handbooks in favor of new methods for organizing medical knowledge. We see this anxiety over individual differences not only in the works of the cosmological doctors but also in texts such as On Regimen in Acute Diseases, Prognostic, Airs Waters Places, and the seven books of Epidemics. In all of these texts, medical inquiry is defined, quite generally, as a search for commonalities. Doctors in this period were gathering together multiple accounts, noting the similarities and differences between those accounts, and isolating high-level generalizations that can unite and govern them all. Although the cosmological doctors took their search for commonalities farther than some of their contemporaries might have been willing to follow, they nevertheless responded to the same pressures that transformed nearly all the medical literature that survives from this period.

The account of the best life for humans, that is, of happy or flourishing life, was the central theme of ancient ethics. This book addresses other important questions about the value of life that likewise received much discussion in antiquity: What does it take to have a life that, if not happy, is at least worth living, in comparison to being dead or never having come into life? Does every human life have some non-instrumental value that makes it worth living? And do all lives that are worth living for those who live them also have to be meaningful, in the sense of making a positive contribution to other humans or world at large? In reconstructing, for the first time, philosophical engagements with these questions from a range of ancient philosophers, from Socrates to Plotinus, the work offers a fresh narrative of ancient ethics. It explores these views against the background of the pessimistic outlook on the human condition adopted by the Greek poets, but also points out continuities and contrasts between the ancient perspective and modern philosophical debates about related themes in biomedical ethics and in the ethics of procreation.

This chapter focuses on Neoplatonist engagements with the issue of life worth living as represented in the philosophy of Plotinus. The Platonic metaphysics and ethics regards the highest form of life as the life of pure intellection, and the materiality of the body in strongly negative terms as the limiting and potentially corrupting influence on the soul. Therefore, the question about the conditions of a life worth living emerges specifically as a question about the worth of embodied life. Is it worthwhile for the immortal soul to descend into bodies, and to remain there until the bond between body and soul dissolves naturally? Plotinus’s attempts to answer this questions are best viewed in terms of a negotiation between the anti-corporealist stance, according to which disembodied existence is always better for the soul, and an acknowledgment that the embodied condition is good for the soul, insofar as it enables the realisation of some of its capacities.

The Stoics break with Plato and Aristotle, who envisaged the value that makes a life worth living as a degree or part of the value that makes a life happy. Instead, they establish two separate axiological scales, one that determines whether a life is happy, and another one that determines whether it is worth living. The former contains virtue and vice, or what is good and bad, whereas the latter is defined by the so-called preferred and dispreferred indifferents, such as health, wealth or renown. This allows for the possibility that a virtuous and happy person sometimes ought to depart from life, when they do not have a prospect of a life worth living, while a vicious and unhappy person ought to stay alive, when they have such a prospect. This decoupling of the happy life from the worthwhile life is consistent with the Stoic view that life itself is a preferred indifferent, and hence the deliberations about staying alive should be referred to other preferred indifferents rather than to virtue and vice.

In contrast to Plato, Aristotle allowed and argued for the possibility that all human lives have some non-instrumental value. This valuation of life is premised on his teleological conception of nature: insofar as all human lives are natural ends of some sort, they are thus a good. However, this non-instrumental value of mere living is in itself not sufficient to make a life worth living. As in Plato, whether a life is lived well or badly is the decisive factor, and again the state of virtue or vice is the most important consideration. Vice makes a life worse than death, regardless of the other good things in it, but fully fledged virtue is not necessary for a life worth living. In contrast to those who are fully virtuous, other non-vicious humans may need other goods, or at least freedom from other bads, such as serious illness or grave misfortunes, to pass the threshold of a life worth living. In contrast to Plato, Aristotle is less optimistic about the chances of the non-educated elite having a life worth living, though he does not flatly deny that possibility.

Focusing on the Republic, this chapter argues that Plato regards psychological health, or the virtue of justice, as the necessary – and sufficient – condition of a human life worth living. This healthy condition amounts to a good exercise of soul’s function (ergon), which is premised on a good exercise of an individual’s function, or job, in the city. This account allows even peasants or craftsman in Plato’s ideal city to have a life worth living, even though they fall short of the best possible human life lived by the rulers-philosophers. It is argued that this non-elitist account of a life worth living is compatible with the famous claim from Plato’s Apology that an unexamined life is not worth living for humans. For in the ideal city all citizens live an examined life, at the very least in the sense of being ruled by the wise philosophers. At the same time, Plato decisively denied the possibility that the mere fact of being alive, or the fact of having a soul, would be a good. It can be a good, if a life is lived well, or it can be an evil, if a life is lived badly.

This chapter examines two versions of hedonist theories of the life worth living, one rather pessimistic, adopted by the Cyrenaics, particularly Hegesias, another more optimistic, adopted by the Epicureans. Both these approaches tend to diminish the gap between the best possible life and a life at least barely worth living, though they do so in converse directions. According to Hegesias, the best possible life falls to the level of a life just barely worth living, that is, a life in which there is no more pain than pleasure. According to the Epicureans, the threshold of a life at least barely worth living is raised to the proximity of the best possible life. A happy life, that is, a life of pleasure, must be a philosophical life, since only philosophy can guarantee freedom from disturbance. But freedom from disturbance is also required for a life worth living, so that a life is not worth living unless it is guided by philosophy, with the important caveat that a progress in philosophy, or the promise of such a progress, is sufficient for a worthwhile life.