Led by Spinoza
About this course
The seventh module of the Metaphysics paper asks how many fundamentally different kinds of thing there are — and what "substance" finally comes to. It is led by Spinoza, whose whole philosophy was built by taking Descartes's answer and collapsing it.
Descartes had split reality into two substances, mind and matter, defined by opposite natures — and was left unable to say how the unextended mind and the extended body could possibly act on each other, a problem his pineal-gland proposal only relocated, and which Princess Elisabeth of Bohemia pressed him on relentlessly. Spinoza's response was radical: deny the premise. There are not two substances but exactly one — infinite, self-caused, necessarily existing — which he calls God or Nature. Mind and body are not two things needing a bridge; they are one and the same thing expressed under two attributes, thought and extension, running in perfect parallel because they are identical. The mind-body problem does not get solved; it disappears. The module sets this against the alternatives — dualism, materialism, idealism — and counts the steep price of Spinoza's cure: a necessary world, an impersonal God, no free will of the ordinary kind.
The student leaves able to reconstruct the real distinction and the interaction problem, to demonstrate Spinoza's one-substance thesis and his parallelist solution, and to navigate the whole map of positions on mind and matter. They read Spinoza's Ethics (Part I and the opening of Part II) and Descartes's Meditations directly.
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Led by Spinoza
The question
Are mind and matter two fundamentally different kinds of substance, or one? Descartes argued they are two — a thinking thing and an extended thing, really distinct — and then could not explain how they interact, since they share no common nature. Spinoza cut the knot by denying there are two substances at all: there is one, God or Nature, and mind and body are merely two aspects of it, which is why they correspond perfectly without ever needing to act on each other. The module follows the argument from Descartes's dualism through its fatal interaction problem to Spinoza's single substance, and asks the student to weigh the whole field of answers — two kinds of stuff, one physical, one mental, or one that is neither — and what believing each would cost.