Fundamental to Spinoza’s philosophy is the idea of substance as “that which is conceived through itself.”

But it’s hard for me understand the content of this phrase. What does it mean, for something to be conceived through itself? I feel like any example of a “conceiving through” that I can wrap my head around is of something that may be conceived through another thing, not a thing conceived through itself. This makes me wonder if the idea of that which is conceived through itself is a cognitively empty notion.

What would Spinoza/Spinozists make of this reaction? I’m sure they would insist that, no, the idea of substance is not cognitively empty - but what, then, is its content?

  • 1
    Following Maimonides, Spinoza defined substance as "that which is in itself and is conceived through itself", meaning that it can be understood without any reference to anything external. Being conceptually independent also means that the same thing is ontologically independent, depending on nothing else for its existence and being the 'cause of itself' (causa sui)... Indeed it's somewhat abstract and difficult to understand. Steven Nadler once commented that a thorough understanding of this definition can directly reach Spinoza's famous core idea... Commented May 23, 2022 at 2:27
  • See Accident: an "accident" is a property of something, like color or age. A property needs a "something" to be conceived. The "something" is substance. Commented May 23, 2022 at 7:14
  • See Spinoza's Ethics: "“On God” begins with some deceptively simple definitions of terms that would be familiar to any seventeenth century philosopher. “By substance I understand what is in itself and is conceived through itself”; “By attribute I understand what the intellect perceives of a substance, as constituting its essence”; “By God I understand a being absolutely infinite, i.e., a substance consisting of an infinity of attributes, of which each one expresses an eternal and infinite essence.” " Commented May 23, 2022 at 7:31

3 Answers 3


I have no precise reference handy but here is my understanding of it after reading Spinoza's complete works and a bunch of commentary books.

Substance in Spinoza's Ethics is all that there is in every possible way it can be conceived. It has an infinity of attributes (ways it can be conceived) but we can perceive only two of them, the extension (our bodies and the physical world around) and ideas.

Since it is all that exists, it's existence is self explanatory (we wouldn't be there to say it does not exist if it really didn't).

For the same reason, it has to be cause of itself, because if some external cause existed it would have to be part of it. Any sentence like "God created the substance" makes no sense since God, as an existing being, is already part of the substance.

And since, as we saw earlier, it encompasses not only the cosmos, but every idea there is to be had about the cosmos, and every idea about these ideas and so on, every idea that we could have about it is also part of it. Thus, "it can be conceived only through itself", it is to say with ideas that are part of it.


An attenpt at deriving Spinoza's claim.

(1) Substance is that which exists by itself and in itself , that is, substance is that which is not an accident [ tradtional definition coming from Aristotle] .

(2) Only one thing can exist by itself and in itself ( = unicity of substance) [ Spinoza's claim]

(3) The unique substance is not only per se and in se , but a se , so to say, " from itself" ( since here is nothing out of it from which it could come; meaning that the unique substance is God).

Note : " aseity" ( = being a se) is a traditional property of God.

(4) Being a se , God ( = substance) is cause of itself [ Spinoza's heterodox understanding of God's aseity] .

(5) If X is cause of Y, then Y has to be conceived through X ( = the effect has to be conceived through its cause)

(6) Therefore, God is to be conceived through itself, i.e. God is conceived through the idea of its infinite essence; in particular, its existence is conceived as a logical consequence of its essence.


Take a substance. Let's say, wood. The point that Spinoza is making is that wood is not understood by understanding something else that's not wood. So, it's not that you understand organic chemistry, or physical particles, and by understanding that you can arrive at a conception of wood. In order to understand wood, you simply have to start with wood itself. This is the meaning of something being conceived through itself alone.

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