PHIL 110 · Metaphysics — Monism and Dualism

Led by Spinoza

The seventh module of the Cambridge Part IA Metaphysics paper, led by Spinoza. How many fundamentally different kinds of thing are there? Descartes says two — mind and matter — and is left unable to explain how they interact. Spinoza answers by collapsing the distinction: there is exactly one substance, God or Nature, of which thought and extension are two aspects, so the mind-body problem dissolves. The module weighs dualism, monism, materialism, and idealism, and what each must pay.

1. Module 7 ○ Open

   One World or Two: Monism and Dualism

   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.

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