 Unsurprisingly, Spinoza does not treat causation as a metaphysical primitive. Instead, he provides an account of causation in terms of something else. In Id1, Spinoza defines self-causation (causa sui) as “that whose essence involves existence or [sive] that whose nature cannot be conceived except as existing.” (Spinoza’s sive should not be read in a disjunctive sense, nor is it usually stating a mere equivalence. What follows the “or” is often a fuller account of what precedes it. Think of it as an “or better yet…”) Expanding his definition to cover causation in general, Spinoza’s idea is that causation is a matter of “involvement” or conceptual connection. If x causes y, this fact obtains in virtue of a conceptual connection between the concept of x and the concept of  y.[3] Spinoza frequently suggests that the conceiving through relation is the paradigm of explanation (e.g., Iax5, IIp5, IIp7s). If so, then we can understand why Spinoza thinks causes serve as sufficient explanatory reasons for facts about existence. If causal relations are conceptual relations, and if conceptual relations are paradigms of explanation, then to give an account of an object’s existence in terms of its causes is to explain the fact that it exists in just the way the PSR demands.