This eye has the pupil of the most holy Faith, which light of faith enables the soul to discern, to know, and to follow the way and the doctrine of My Truth—the Word Incarnate; and without this pupil of faith she would not see, except as a man who has the form of the eye, but who has covered the pupil (which causes the eye to see) with a cloth. So the pupil of the intellect is faith, and if the soul has covered it with the cloth of infidelity, drawn over it by self-love, she does not see, but only has the form of the eye without the light, because she has hidden it. --St. Catherine Siena Dialogue