What Advantages Does Spinoza’s Substance Monism Have over Descartes’ Dualism?

Spinoza’s philosophy as espoused in the Ethics was a response to Descartes’ dualism. Through works such as the Ethics, Spinoza seeks to address the main flaws in Descartes’ philosophy.
These flaws included but were by no means limited to, proof for the existence of God and the interaction between mind and body.
This essay will highlight the advantages of Spinoza’s monism over Descartes’ dualism by looking at Spinoza’s response to these issues.
First, in order to consider the advantages of Spinoza’s substance monism over Descartes’ dualism it is necessary to show how each philosopher demonstrates their substance dualism or substance monism.
Tim Crane defines monism and dualism as follows: “Monism denies that minds and their bodies are distinct substances. Monists assert that substances are all of one kind. They could say that all substances are mental; or they could say that all substances are bodily […] Dualists hold that minds and bodies are capable of independent existence.”
Although the concept of dualism can be traced back to Plato, it is generally recognised that modern versions of substance dualism have their origins in Descartes’ Meditations on First Philosophy, first published in 1641.
In the Sixth Meditation Descartes’ states that:
It is true that I may have (or, to anticipate, that I certainly have) a body that is very closely joined to me. But nevertheless, on the one hand I have a clear and distinct idea of myself, in so far as I am simply a thinking, non-extended thing; and on the other hand I have a distinct idea of body, in so far as this is simply an extended, non-thinking thing.
Descartes’ distinction here is between two types of substance, extended corporeal substance, res extensa and non-extended thinking substance, res cogitans. If one is to include God in Descartes’ theory on substance, then it could be considered that his ‘dualism’ allows for three substances; or as has been pointed out, God is Descartes’ only substance

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