In book XII of his Meditations, Marcus Aurelius writes:
People ask, ‘Have you ever seen the Gods you worship? How can you be sure they exist?’
i. Just look around you.
ii. I’ve never seen my soul either. And yet I revere it.
That’s how I know the Gods exist and why I revere them — from having felt their power, over and over.Marcus Aurelius, Meditations 12.28 (trans. Hays)
There are at least two noteworthy things here. First, and most apparently, we see the deep and genuine piety of this Stoic thinker and ruler of the known world, expressed eloquently and movingly. Put this passage alongside others from the Meditations, including the beautiful words of thanks in book I, and we see beyond a shadow of a doubt that for Marcus, the Gods are real, powerful, active presences in his life.
Second, and more subtly, in the analogy to the human soul, we see the Stoic doctrine of the subtle fire which animates all of the more gross matter in the cosmos. On this view, the human soul is supposed to be sure a fire, permeating the body, giving it vitality and motion. When that fire goes out, the body is dead, meaning that it is no longer self-maintaining, no longer an organic unity. Likewise, at the level of the cosmos as a whole, it is the creative fire of divine intellect—so frequently identified by the Stoic philosophers with Zeus himself—which animates and brings to perfection the entire order of the universe, which is likewise a perfect unity. Marcus’ answers, then, are not mere arbitrary comparisons, for which others might just as well be substituted, but are rooted in a core doctrine of Stoic metaphysics.
It’s not my preferred mode of doing metaphysics. I tend toward a bit more transcendence, and I’m less eager to shoehorn all of what’s real into what’s material. Nonetheless, I can appreciate both the general Stoic approach, and the way in which that approach can ground a deep and genuine piety.