Spinoza's Ethics: IIP.42

This proposition build on the objective truth of the prior proposition to the power of the act of understanding as it operates. The demonstration hints at a proofing issue similarly embedded in today's cliche IYKYK. To those for whom the distinction is not evident through itself, this issue is difficult to prove as there is likely to be a self-referencing issue. This is a criticism that is also repeatedly asserted at Spinoza and his framework.

Secundi et tertii et non primi generis cognitio docet nos verum a falso distinguere.

Knowledge of the second and third and not the first leads us to distinguish true from false.

DEMONSTRATIO: Hæc propositio per se patet. Qui enim inter verum et falsum scit distinguere, debet adæquatam veri et falsi habere ideam hoc est (per II scholium propositionis 40 hujus) verum et falsum secundo aut tertio cognitionis genere cognoscere.

This proposition is evident through itself. For the person who knows how to distinguish between true and false, ought to have an adequate idea of the true and the false, that is (by IIP40S) to know the true and false by means of the second and third kind of knowledge.