Metaphysical theories heavily rely on the use of primitives to which they typically appeal. I will start by examining and evaluating some traditional well-known theories and I will discuss the role of primitives in metaphysical theories in general. I will then turn to a discussion of claims of between theories that, I think, depend on equivalences of primitives, and I will explore the nature of primitives. I will then claim that almost all explanatory power of metaphysical theories comes from their primitives, and so I will turn to scrutinize the notion of "power" and "explanatory"