 Wolff’s most extensive treatment of the PSR appears in §§56–78 of his Ontologia. In this discussion, Wolff appears to give two separate accounts of the theoretical origin of the principle. On the one hand, in §70, Wolff provides a proof (or derivation) of PSR from PC and the notions of “something” and “nothing”. And, on the other hand, in §74, Wolff claims PSR is a principle of the human mind and a self-evident logical axiom. Although prima facie, it is unclear why Wolff attempts to advance both views, it is perhaps worth pointing out the difference between (1) being able to be demonstrate the truth of a proposition and (2) knowing the truth of a proposition because it is self-evident. While demonstrating the truth of a proposition yields knowledge of it, to know a proposition because it is self-evident may or may not mean the proposition is also demonstrable. There is no inconsistency, for example, in holding that one and same proposition is both self-evident and demonstrable. A proposition could be known immediately one way and yet, in another way, follow as a conclusion of a sound deductive argument.