The Republic by Plato Part 6 Page 91

You have quite conceived my meaning, I said; and now, corresponding to these four divisions, let there be four faculties in the soul — reason answering to the highest, understanding to the second, faith (or conviction) to the third, and perception of shadows to the last — and let there be a scale of them, and let us suppose that the several faculties have clearness in the same degree that their objects have truth.

I understand, he replied, and give my assent, and accept your arrangement.