The most devastating objection against Spinoza's thesis that there is only one substance in the universe is that raised by his contemporary Simon De Vries: If substance has an infinite number of distinct essences and substance is identical to its essence, how can there be only one substance?
The majority of Spinoza scholars have considered De Vries’ objection an insoluble problem. Joachim, for example, has stated:
We must therefore admit that there is a serious defect in Spinoza's general theory of the nature of Reality. The unity of Substance which seemed so absolute — the unity which was more than the unity of a system — resolves itself into a mere ‘togetherness’ of an infinite multiplicity. The Reality falls apart into a substratum without character …