Spinoza's Argument for Substance Monism and Common Objections

Spinoza’s Argument for Substance Monism and Common Objections

Spinoza’s Ethics is widely thought of as Spinoza’s greatest work. One noteworthy claim that he makes in his Ethics is his argument for substance monism, or the existence of only one substance. In Proposition 14, Part I of his Ethics, Spinoza states that “There can be, or be conceived, no other substance but God.” This statement amounts to saying that everything else in this world, whether it is extended or not, is a mere image of God. Spinoza’s proof for this comes in three steps. One, assume that no two substances can share an attribute. Two, assume that there exists a substance that contains infinite attributes. Three, by these two assumptions, another substance cannot exist because it would have to share an attribute with God. Although there are objections claiming these assumptions and, consequently, the proposition are wrong, these objections are based on misinterpretations of Spinoza’s definitions, and I believe Spinoza is correct in arguing for substance monism. In order to prove my point, I will first define some terms and give some axioms that Spinoza uses. Then I will prove the two assumptions he uses in his proof, and argue for substance monism. Afterwards, I will proceed to give the most common objection to Spinoza’s proof, followed by a refutation of this objection.

In the beginning of his Ethics, Spinoza gives the definitions and axioms that all of his propositions are based on. Spinoza defines a substance to be that which is in itself and is conceived through itself. A mode is defined as the affections of substance (we will use the term affections in place of modes.) An attribute is that which the intellect perceives of substance as constituting its essence. For example, if we assume a tree to be a substance, an attribute is what we perceive to be the essences of the tree, and pine, maple and willow would be some of the many modes of trees. In reality we would not consider a tree to be a substance because it is not in itself, but attributes and modes could be similarly interpreted. Define God to be a substance containing infinite attributes. Proposition 7 states that existence belongs to the nature of substance because substances cannot be produced by anything else, and thus must be self created, necessitating their existence. Proposition 3 states that things must have some things in common to have caused the other.

Now we will move on to the first part of the proof of substance monism. We will first prove the first assumption that no two substances can share an attribute. The proof of this argument can be found in Proposition 5, Part 1 of Spinoza’s Ethics. He first argues that outside the intellect there exist, by definition, only substances (which are in essence attributes) and modes, and thus we can only distinguish substances based on these two criteria. Thus we can assume that two or more distinct things can be distinguished from one another either by a difference of the attributes or by a difference of affections (proposition 4, part 1.) To begin, consider the first part of the assumption and suppose that we can distinguish two substances only by a difference in attributes. If so, the two substances would have to have different attributes to begin with, and in this case two different substances will not have a common attribute. Thus, when distinguished by a difference in attributes, two substances cannot share an attribute. Next, we consider distinguishing substances through affections. Assume that there are two substances that have different affections. However, substances are prior to affections, and thus substances cannot be conceived through affections. Therefore, even if we could distinguish between two different affections, it would not necessarily say anything about the substances in themselves. Thus, we cannot distinguish between substances just by their affections. Thus, substances can only be distinguished by attributes, in which case no two substances can share an attribute.

The second assumption Spinoza makes in proving substance monism is that God exists. Spinoza gives many proofs for this, I will only give one. It is given that for every thing there must be a cause or reason for its existence or non-existence. It is also given that this reason must be inside, or outside the thing being considered. Suppose God does not exist. The reason for this must be inside or outside God. First, if the reason is inside God, it goes against our definition of God as a substance because substances necessarily exist (Proposition 7.) Thus the reason is not inside God. Second, if the reason exists outside God, then we would be implying that a thing outside of God exists that is causing God’s non-existence. This thing that explains God then necessarily has the same nature as God because if not, it could not be the cause of God (Proposition 3.) But if it does have the same nature, we would consequently be claiming that God exists because this thing outside of god will identical to God. Thus, no matter where the reason for God’s non-existence lies, we cannot prove that God does not exist, and therefore God must exist.

So far we have proved that no two substances can share an attribute and a substance containing infinite attributes necessarily exists. From these two facts, Spinoza claims that there can be only one substance in this world, and that the single substance is God. However, many people object to this claim. These objections are not based on the logic of the proposition itself, but rather on the premises of it. I will first state one of the more common objections. Then