Nothing exists of which it cannot be asked, what is the cause (or reason), why it exists.
Spinoza: Sufficient Reason
The Principle of Sufficient Reason (PSR) stipulates that everything must have a reason, cause, or ground. Spinoza would add to the epigraph above that since “existing is something positive, we cannot say that it has nothing as its cause. Therefore, we must assign some positive cause, or reason, why [a thing] exists—either an external one, i.e., one outside the thing itself, or an internal one, one comprehended in the nature and definition of the existing thing itself.”1
Spinoza in Axiom 7 appeals in his explanation – previously stated, that it is a variant of the “ex nihilo, nihil fit” (“from nothing, nothing comes”) principle, and stipulates that an existing thing and its perfections (or qualities) cannot have nothing or a non-existing thing as their cause. So would this for Spinoza preclude any form of relation with an inexistent? We know that in the Treatise on the Emendation of the Intellect, Spinoza allows for one unique item to be without a cause. In §70 of this treatise, Spinoza argues:
[T]hat Thought is also called true which involves objectively the essence of some principle that does not have a cause, and is known through itself and in itself. (II/26/33–4.)