The Uncaused Cause of theism is distinct from the many polytheistic gods, for there cannot be more than one unlimited existence as such. More than the Most is not possible. Such a Cause is Pure Actuality, and Actuality is unlimited and unique. Only act as conjoined with potency is limited, such as is found in contingent beings (which exist but have the possibility not to exist).
Further, in order to differ, one being would have to lack some characteristic that the other one had. But any being that lacked some characteristic of existence would not be an unlimited perfect existence. In other words, two infinite Beings cannot differ in their potentiality, since they have no potentiality; they are Pure Actuality. And they cannot differ in their actuality, since Actuality as such does not differ from Actuality as such. Hence, they must be identical. So, there is only one Unlimited Cause of all limited existence.