The Epicureans believed that life was at the mercy of atoms in motion. Ataraxy (happiness, but more literally “unruffledness”) meant just that one could marry and have children, attend religious services if one so chose, or that one could be a kindly neighbor. But with life being matter, the only real gauge of conduct was pleasure, defined simply as an absence of pain. Philosophers such as Epicurus and Lucretius did attempt to advance the idea that within their material ontologies an element of “swerve” was at work, one that could initiate new causal chains and thus enable something like real ethical choice. Their goal was to break logical and physical determinism and to make room for human freedom and an ethical human will. However, this turned out to be problematic. For thinkers such as Epicurus and Lucretius, we cannot hold our will morally responsible in any ultimate sense simply due to the nature of the material causal chain in place in the cosmos (this despite the swerve, their dictum being “wherever pleasure leads us.”) One may live an ethical life, but its ultimate significance is meaningless given the finality of death and the nature of a cosmic void. Of course here the crux of my analysis hinges on the word “ultimate.”
As I see it, one need not invoke traditional ultimates, for example rewards for goods or punishments for evils in an afterlife, in order to save ethics or to save something like valuation (i.e. “good” and “evil” – or value claims in general, for that matter). The Stoics, as opposed to the Epicureans mentioned above, did admit a place for ultimacy in the universe, but that sense of ultimacy did not center on otherworldly reward and punishment. For the Stoics, rather, nature was an ultimate, conducive with a guiding principle of reason that struggled toward consummation. Thus, nature, on the Stoic view, was not just material, but said to include reason (as a sufficient principle and logos): a manner of accessing the ultimate. Reason, being fully natural (specifically human reason, but reason was also taken to be a ubiquitous principle and thus presumably it permeated the world) was thus said to be essential for ataraxy. Ultimacy for the Stoics was the peculiar potential of the human as a distinct creature (not a superior creature) to achieve ataraxy by means of autarky, by identifying one’s self with nature and by using reason. Being a natural being and a rational being were said to be one. Thus, reason takes on a special (for the Stoics “divine”) significance. And so a similar, but much better picture than the Epicurean one, in my judgment, is offered by the Stoics.
For the Stoics, autarky or self-sufficiency is compatible even within a material ontology in place. And by identifying with nature, the Stoics took the view that behavior was “as nature would have it.” For some this would be called Stoic apathy. But in this particular sense apathy is not listlessness but rather “imperviousness to perturbations.” Even death is not a mute end, blank or representative of void (as in the material ontology), death is in accord with nature being fully part of it, and hence being natural it is rational (even hastening death if it prevents enslavement and preserves autarky is more “natural” and "rational" than attempting to compromise natural forces). With this in mind, while sharing a similar physics, the Stoics therefore had a superb use of reason, logos, or account of nature and the universe, when it came to ethical issues.
Finally, for the Stoics, the universe, while including spontaneity, also included accrued (statistical) order. Order arises from tendency (i.e. Leibniz), and for the Stoics such a tendency creates world cycles, each struggling to consummate itself (something like Whitehead’s cosmic epochs). Moderation was the order of the Stoic outlook - there was no room for radical self-sufficiency where the individual was set to somehow "defeat nature's way." Individuals were just that, individuals in a rational, but also tragic, universe. With this idea the Stoics wanted to enjoin "life in accordance with nature," and not assert any form of self-sufficiency against it. For this reason life in accordance with nature was inevitably tragic as our ordering of the world may not necessarily be nature's ordering of the world.
Seneca's writings stand out as the most profound to me, but also Epictetus. Both were sensible toward weakness and misery, as well as pain. Ethical disorder in an ordered cosmos meant that pain and suffering have their part, if real spontaneity was true. Unity and order, coupled with reason, shows that the human being may accustom itself to conditions and circumstances *ultimately* beyond human control. Whose control, then? But first, a second question.
Fate, providence, as well as deity became ever important for the Stoics. Philosophy was at times little more for them than reconciling the inevitable. But how is reconciling the inevitable, accepting "nature's way" or fate, apathy, better than the materialist ontology of pleasure and pain as found in the Epicureans?
The answer to both questions here is that, like Buddhism, the Stoics thought that the power behind ethics is within our own "self control," and so autarky comes to mean choosing to control those impulses which attempt to defy the material and natural world, and this is what allows us to remain indifferent to illness, pain, and death. In other words, indifference is within our control because it is internal as a matter of self impulsion. With the guided use of reason, one may properly respond to life through simply internally responding to - by choosing to accept - a world that "makes us." Like Buddhism this is not to shun the dark and painful features of life, or to shun the natural (and rational), material world. Rather, it is to accept things as they are, fully natural and material, but also to act with a reason present within, as a matter of choice and ethical living, as fully natural beings, to be enlightened as to the true nature of things distinct from our distortions of them (a goal of realist metaphysical query).