 The second implicit premise of Spinoza’s argument for the claim that all possible substances necessarily exist is that causes provide (or just are) necessary and sufficient explanatory reasons. This idea appears in the previously quoted passage in which Spinoza claims that citing a “cause or reason” suffices for explaining facts about the existence and non-existence of a triangular object. Applied to the case of substance, the sufficient reason for why a substance exists is supplied by the causes of that substance.