P41: Knowledge of the first kind is the only cause of falsity, whereas knowledge of the second and of the third kind is necessarily true.

Dem.: We have said in the preceding scholium that to knowledge of the first kind pertain all those ideas which are inadequate and confused; and so (by P35) this knowledge is the only cause of falsity. Next, we have said that to knowledge of the second and third kinds pertain those which are adequate; and so (by P34) this knowledge is necessarily true.