In Proposition 7, Part I of the Ethics Spinoza claims:
Existence belongs to the nature of substance.
This means that substance exists necessarily or, to put it even simpler, that each substance must be it's own cause (i.e. "causa sui" - see the proof of proposition 7). What do other philosophers think of this? I'm particularly interested in the views of Aristotle, Descartes and Medieval philosophers on the necessary existence of substance (or on the views of other philosophers who wouldn't accept Spinozas doctrine that substance exists necessarily). Is it a universally accepted doctrine or are there philosophers claiming that existence does in fact not belong to the nature of substance? If someone does, which consequences would follow from the rejection of Spinozas claim? Would it oblige them to grant the possiblity of non-existent substances? Or would any of them see substances not as themselves existing but only as something giving rise to existence? Or would any of them allow for one substance to bring another into existence? Or would they consider some substances as existing and others not? Or rather none of these consequences? It would be helpful if anyone could inform me on the issue.
Note: I know that Spinoza transforms the meaning of Substance profoundly in that he does conceive of substance in the singular, while the mentioned philosophers in general think about substances, i.e. in the plural, which means it is usually granted that there is a multiplicity of substances, while for Spinoza there is only one. Anyway, it would be nice if anyone could inform me on any position that rejects the view that substance (or substances if you will) exist(s) necessarily.