 Let us apply this point to the case of substances. Spinoza reasons that existing substances exist in virtue of having causes that bring about and explain their existence, and non-existing substances do not exist in virtue of causes that prevent their existence and explain their non-existence (Ip14). According to Spinoza’s account of causation, this means that existing substances exist in virtue of conceptual relations to whatever explains their existence, and, similarly, conceptual relations explain the non-existence of non-existing substances. What causes or explains the existence or non-existence of a substance?