Section I.

I. Wherein is the Criterion for the Apprehension of the Soul.

All things that exist are either known by sense or apprehended by thought. And what falls under sense has its adequate demonstration in sense itself; for at once, with the application, it creates in us the impression of what underlies it. But what is apprehended by thought is known not by itself, but by its operations. The soul, consequently, being unknown by itself, shall be known property by its effects.