 Of course, that reasoning relies on possible world semantics and some loaded (though plausible) theses about relations between possible worlds. Perhaps Spinoza could reach a similar conclusion without recourse to all that. Spinoza could instead appeal back to his plentitude principle and its basis in the PSR. If there could have been more infinite modes than there in fact are, these non-actual, merely possible modes must be compossible with the collection of necessarily existing infinite modes. (Another plausible assumption, expressed loosely: if something is not compossible with what necessarily exists, then its existence is not possible.) But if there were non-actual infinite modes that were compossible with the collection of necessarily existing infinite modes, what could explain their non-existence? Unless an answer can be given, Spinoza will infer falsity from a violation of the PSR. We again reach the conclusion of necessitarianism with respect to every infinite mode. Like substance, every possible infinite mode necessarily exists.[9]