Why does Spinoza think Unity is a necessary property of substance? Is this something he posits or is there an argument behind this?

1 Answer 1


Here's a basic answer :

Spinoza's account is inextricably linked to the one substance and its essence. "All things ... are in God, and everything which takes place takes place by the laws alone of the infinite nature of God, and follows ... from the necessity of His essence" {Ethics, I, prop. XV, dem.). But according to Spinoza, substance is not essence, so an explanation of Unity in terms of substance as essence is not possible. It has an essence, and other things have essences too. Thus, Spinoza can say that unlike substance whose "essence necessarily involves existence, or, in other words, it pertains to its nature to exist" {Ethics, I, prop. VII, dem.), "the essence of things produced by God does not involve existence" {Ethics, I, prop. XXIV). For Spinoza, Unity consists of, or is based upon, one infinite substance or God whose essence is existence and from which everything necessarily follows. Unity is connected with substance and essence in such a way that it is difficult to see how one can even approximate Spinozistic Unity apart from substance and essence. (Michael P. Levine, 'Pantheism, Substance and Unity', International Journal for Philosophy of Religion, Vol. 32, No. 1 (Aug., 1992), pp. 1-23 : 15.

Levine could be clearer but the main point is that while Aristotle, for instance, recognises a plurality of substances, Spinoza acknowledges only one, infinite substance which calls 'deus sive natura' - 'God or nature'. He does not believe that more than one entity can satisfy his definition of substance as 'that which is in itself and is conceived through itself'(Ethics, I, Definition 3). If there were more than one substance, the nature of each substance would have to be conceived - specified - in terms of its relation to the other substance(s). E.g., through the spatial relation of one substance to another, of their causal interaction or independence, of their similarities and differences. No substance could be 'conceived through itself' but only through its relation to another substance or other substances, whose existence would condition its own. This would violate the definition of substance.

Difficult, obscure matters but I hope this throws some light.

  • Hi, thanks for the answer but I actually meant to ask this question for Leibniz, and Spinoza was a typo. Here is the question I meant to ask. Sorry for the confusion...hopefully this question is useful to someone in the future though. philosophy.stackexchange.com/questions/52987/…
    – Robert C
    Commented Jun 11, 2018 at 5:44
  • @Robert C. No problem. These things happen. I have even been known to make typos myself ;)- I see Mauro has already given a v. good answer on Leibniz. Best - GT
    – Geoffrey Thomas
    Commented Jun 11, 2018 at 8:11
  • Nice answer! This seems a vital issue since it clarifies the point that if the universe is a unity then mind-only and matter-only theories are wrong, In metaphysics we discover that they don't work which is suggestive and implies the unity of the universe. Leibnitz notes that a unity has no parts which would mean that a fundamental theory must reduce extension and we would end up where Kant ended up, most of the way to Plotinus and the perennial view of the Unity of All and the metaphysical unreality of time and space. .
    – user20253
    Commented Jun 12, 2018 at 18:49

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