Substance
Substance is what exists in itself and is conceived through itself. For Spinoza, there can be only one substance — God/Nature.
In depth
Spinoza defines substance as that which requires nothing else to exist or be understood. Unlike Descartes, who allowed multiple substances (mind, body, God), Spinoza argues there can only be one. If two substances existed, they would need to differ by attribute — but a substance with infinite attributes leaves no room for a second. Everything else is a modification (mode) of this one substance.
Why it matters
By reducing reality to one substance, Spinoza eliminates dualism at the root. Mind and body are not separate things but different expressions of the same reality. This move grounds his entire system.
Source references
- Ethics I.P1-P8
Connected concepts
Appears in paths
Substance
In-itself / in-another split
Substance is prior to its modifications
No two substances can share an attribute
One substance cannot be produced by another
Existence belongs to the nature of substance
Every substance is necessarily infinite
God necessarily exists
Besides God no substance can be conceived
Whatever is, is in God
Things could not have been produced otherwise