Overview

Spinoza seeks to establish these things.

1. Monism: there is only one substance, God or Nature

2. Pantheism: everything in nature is part of God

3. Determinism: everything is wholly determined

4. Parallelism: the one substance has infinitely many attributes that do not interact with one another but are “parallel” with each other. (e.g. mind and body)

We only covered the first two: monism and pantheism.

Background on substance

One problem with the term “substance” is that it is used by different philosophers for different purposes and with different meanings. Fun! So here is some background on substance and the related concept attribute. For passages that illustrate these uses, see the handout.

First, substance is used to draw a distinction between what things are and what we can know about them. Substances are what things are and attributes are what we know.

Second, substances are used to identify things and distinguish them from other things. Substances, on this understanding, are things that can exist by themselves because they are not parts of other things. According to Descartes, for instance, a substance is “a thing that is suitable for existing in itself” (Descartes [1641] 2019, 51L).

Third, substances are used to explain identity through change. Here the idea is that substances stay the same while the things that change are the attributes.

Finally, you will see philosophers draw a distinction among attributes between essential attributes, like extension for bodies, and inessential attributes (aka “accidents”) such as the size or shape of a body.

Spinoza on substance

Spinoza focuses on the idea that a substance is whatever can exist by themselves. In a nutshell, he thinks the only thing that can exist apart from anything else is the universe: everything there is. Accordingly, substance is not helpful in distinguishing one medium sized object from another, much less in explaining how one of those things remains the same despite change.

For Spinoza, a substance is “that which is in itself and is conceived through itself; that is, that the conception of which does not require the conception of another thing from which it has to be formed” (Spinoza [1677] 2019, 172L).

An attribute is “that which the intellect perceives of substance as constituting its essence” (Spinoza [1677] 2019, 172L). Note that this means Spinoza is not going to distinguish between essential attributes and inessential ones. All attributes are essential, as he uses the term “attribute.”

Spinoza’s argument

Spinoza’s argument has four steps.

1. Substances cannot share attributes and so cannot interact.

2. An infinite substance must exist

3. An infinite substance has all attributes

4. Therefore, there is only one substance.

Here is a compressed account of this argument.

The first step requires that you accept that only things that share attributes could causally interact with one another. That, in turn, depends on understanding “cause” in an intellectual sense: a cause, as Spinoza uses the term, is something that explains the existence or qualities of its effect. We use the term that way: the 8 ball moved because the cue ball hit it. But for Spinoza, the relevant explanation is logical: it means showing that one true proposition is the logical consequence of another. In this sense, the definition of a triangle causes the sum of the interior angles of such a figure to be 180 degrees.

Substances are understood through their attributes, which, again, are their essential features. Suppose there are two substances.

1. They cannot share attributes because, if they did, they would have the same essential features and so be the same substance not two different substances.

2. But if they have different attributes, we cannot understand how the one could explain anything about the other. This is like Descartes’s problem about the interaction of mind and body, where he cannot explain how one substance could interact with another.

If different substances cannot causally interact, then one substance cannot cause another to come into existence. If there is a substance, it must have caused itself to exist; nothing else could have created it. That means the substance must necessarily exist since one of the things it does is cause itself to exist. Furthermore, the substance must be infinite. If it were finite, something else would have to limit it, but that would require different substances to interact with one another, which we have already ruled out.

Spinoza’s argument that this substance would have to have all of the attributes in Proposition 10 is not an easy argument to follow. If it is granted, the conclusion that there is only one substance would follow. Any other substance would have to have its own attributes, as attributes are not shared. But if the infinite substance has all of the attributes, there are none left over for any other substance. So there can only be one substance.