The deep spiritual practice of Stoicism depends on trust in a providential cosmos. While the concept of providence is not difficult to grasp, many moderns attempting to practice Stoicism will find it difficult to assent to…because they simply do not realize how essential providence is to Stoic ethical theory and practice.
I have never understood the insistence of some on the necessity of providence, god(s), or any other rational agency for the practice of Stoicism. The ethical teachings of Stoicism seem equally accommodating of a providential agent or irrational causal determinacy (or probabilistic determinacy given quantum indeterminacy). The important thing to grasp is that there is a way that the world is, a certain factness that does not heed our opinions, objections or desires. The question that Stoicism seeks to answer is what best to do about these circumstances.
This strange insistence on a providential agent seems largely grounded in the circumstances and beliefs of historical Stoicism. It is argued that since Stoicism developed in a theistic milieu and incorporated these beliefs into the rationalizations for their ethical prescriptions, that they are somehow inseparable from Stoicism. And yet, ancient Stoic philosophers also believed in omens and other forms of divination, they believed in a materialistic physics that described the universe as a sphere composed of four elements (fire, air, earth, and water) drifting through the void. Must I adopt this four element conception of the universe in order to be a Stoic? Should I look to bird entrails to discern what the future holds for me?
The ancient Stoics cared about reason and physics and saw them as being an integral part of their philosophy, important elements that fed into and informed their ethics. I agree with this premise wish to follow their example of looking to reason and science to inform my ethics. But science and reason are not frozen. These are fields that have advanced through thousands of years of human effort and ingenuity, and to then throw this progress away and cling to outdated Hellenistic notions of the world is misguided, foolish, and contrary to the spirit of the enterprise known as Stoicism.
Likewise, I do not need to believe in the providence of Zeus in order to be a Stoic. Stoicism functions perfectly fine with any number of substitutions one might wish to make. Instead of Zeus, you can believe in the God of Christianity or perhaps Allah from Islam. Or you can do away with the concept altogether and believe that trusting in a providential agent that conducts itself in such a fashion as to be indiscernible from a web of interconnected causal events is the same as trusting in nothing, since the belief does nothing other than ascribe the efforts of our brain to find patterns in circumstantial events to the activities of an unseen actor.
All of these appear to me to be perfectly valid beliefs within the framework of Stoic ethics. Determinacy is certainly an important element in Stoicism. But the particular brand of determinacy you bring to the table does not make that big of a difference. To insist otherwise strikes me as dogmatic and in general opposed to reason and the virtues that Stoicism espouses.