Spinoza sought to correct what he saw as a flaw in Descartes' dualism. While Descartes allowed for three substances (God, Mind, Matter), Spinoza argued logically that there can be only one substance.
Spinoza defines substance as "that which is in itself and is conceived through itself." This led him to his famous conclusion: Substance = God = Nature (Pantheism).
"Deus sive Natura" (God or Nature)
If there is only one substance, how do we explain the diversity of the world? Spinoza explains this through Attributes and Modes.
Psycho-physical Parallelism: Since Thought and Extension are attributes of the same substance, they correspond perfectly but do not interact directly. Every "idea" in the mind has a corresponding "event" in the body.
Leibniz disagreed with both Descartes and Spinoza. He argued that the ultimate constituents of reality are not physical matter or a single substance, but an infinite number of spiritual atoms called Monads.
If monads are "windowless" and do not interact, how does the universe appear so orderly? Leibniz proposed the doctrine of Pre-established Harmony.
He used the Analogy of the Two Clocks: God, the perfect clockmaker, created all monads (clocks) to be so perfectly synchronized that they show the same time forever, even though they never touch. This explains how the mind and body appear to interact without actually doing so.
Q: What is the main difference between Spinoza's Monism and Leibniz's Pluralism?
A: Spinoza believes there is only one substance (Monism), while Leibniz believes there are infinitely many substances (Pluralism/Monadology).
Q: Why are monads called 'windowless'?
A: Leibniz meant that no outside force can change the internal state of a monad. Each monad unfolds its own internal program, pre-set by God at creation.
When writing about Spinoza, emphasize his Geometric Method. He tried to prove his philosophy like a math book, using definitions, axioms, and theorems.