The construction of Rationalist Metaphysics.
Spinoza believed that Descartes made a mistake by dividing the world into two substances (Mind and Body). He argued that there can be only one infinite, self-caused substance.
Spinoza’s famous phrase "Deus sive Natura" (God or Nature) reflects his Pantheism. Everything that exists is simply a part of the one divine substance. God is not a creator outside the world; God is the world.
If there is only one substance, how do we explain the difference between a thought and a rock? Spinoza used two concepts:
Parallelism: Mind and Body do not interact. They are like two clocks perfectly synchronized because they are just two different ways of looking at the same substance.
Leibniz rejected Spinoza’s Monism and Descartes’ Matter. He argued that the world is made of an infinite number of simple, spiritual "force-centers" called Monads.
If monads are "windowless" and do not interact, how does the universe work together so perfectly? Leibniz proposed Pre-established Harmony.
God, the master clockmaker, created all monads at the beginning of time to be so perfectly synchronized that when I will my arm to move (Mind), the monads in my arm move (Body) at the exact same moment, without any direct interaction.
| Philosopher | Number of Substances | Relationship |
|---|---|---|
| Descartes | Dualism (2: Mind/Body) | Interactionism |
| Spinoza | Monism (1: God/Nature) | Parallelism |
| Leibniz | Pluralism (Infinite Monads) | Pre-established Harmony |