We are getting near the end of my running commentary on the wonderful Cambridge Companion to the Stoics, this time tackling the Stoic take on naturalism — a term in philosophy that has taken on a variety of meanings over the past two millennia or so.

The relevant chapter, written by T.H. Irwin, begins with a useful reminder of the three Stoic doctrines that have markedly influenced later moral philosophy: “(1) Eudaemonism: the ultimate end for rational action is the agent’s own happiness. (2) Naturalism: happiness and virtue consist in living in accord with nature. (3) Moralism: moral virtue is to be chosen for its own sake and is to be preferred above any combination of items with non-moral value.”

These three doctrines are intertwined as far as the Stoics were concerned: “The correct grasp of human happiness shows that it consists in living in accord with nature, which requires living in accordance with virtue in preference to any other aim,” an approach that they complemented with what is often referred to as a developmental theory of the naturalness of virtue: “In the course of natural development, we come to recognize a special place for virtue. We begin from self-love, directed to our own nature and constitution. To secure the goods we seek for our nature and constitution, we begin to exercise practical reason. But in the course of exercising practical reason, we come to prefer ‘order and concord’ in our actions over the natural goods that we initially seek.”

Irwin contrasts this approach with that of the Epicureans and Cyrenaics, who thought of virtue as instrumental to happiness, and he also points out that the Stoic trio of concepts was in fact inherited and developed by much Christian theology during the Middle Ages (e.g., by Albert and especially Aquinas).

In what sense is the above an instance of “naturalism”? As Irwin puts it: “If some actions are morally right (honestum) because they are appropriate for human nature, we have a natural basis for justice, apart from the usefulness of justice in maintaining a society,” an explanation that also makes sense of the Stoic idea of oikeiôsis, the basis of their cosmopolitanism.

The obvious objection to the Stoic take on naturalism in ethics is that modern mechanistic science does not seem to have room for ethical discourse. “Value” is nowhere to be found in physics, chemistry, biology and so forth. But here Irwin makes an interesting move: “At first it seems obvious that the world-view of physical science has no room for rightness and wrongness. But if we allow that it has room for healthiness and unhealthiness, we may also be convinced that moral properties are constituted by facts about what is healthy or unhealthy, or in other ways good and bad, for rational agents,” which very much resembles Larry Becker’s take in his A New Stoicism.

Please notice that this isn’t a Sam Harris-like, crude equation between scientific fact and morality. The Stoic approach doesn’t make the Humean gap between is and ought magically disappear, but it does provide for a bridge based on naturalistic principles — without which the gap really would be magical (as it is in theology).

Another interesting comment by Irwin relates to the teleology of the Stoic moral system: “This conception of nature may be called teleological, since it refers to a system in which the working of the parts is regulated by the characteristic functions of the whole. But it does not presuppose cosmic teleology, since it includes no claim about how individual things come to be systems of this type.”

I find this particularly interesting as a biologist, since while I don’t believe the cosmos as a whole has a teleological character, I do think that living organisms display the closely related property of teleonomy, as I explained in a recent post at my other blog. This type of teleonomy is not the result of intelligent design, or even of Stoic providence, but rather of the process of natural selection.