I'm not sure about the idea that "Summon Magic" is a part of theurgy … some FRPGs might count it as such, but theurgy is generally about combining religious practice and magic. One does not generally summon one's deity and bark orders … even animist shamen who deal with pretty low powered entities on the scale of "things that get worshipped" tend to find it better to invoke respectfully.
Summoning, if it belongs to "real world" magical traditions at all, seems to be the purview of irreligious academic magicians.
Theurgy / Discussion