Many proofs are offered for the existence of god – most notably the ordered universe proving the existence of a creator with a guiding hand. Stoics also believed that atheism must be false because, if it were true, that would mean that man, with all his faults, is the highest being in the universe -- an illogical conclusion.
With respect to the nature of the gods, the Stoics provide a definition:
God is an immortal living being, rational, perfect and thinking in happiness, unreceptive of anything bad and provident with regard to the cosmos and the things therein. But he is not of human form. He is the demiurge of the whole and as it were the father of all things, both in general and insofar as the part of him is concerned which pervades all things, and which is called by many names, corresponding to its powers.