The Conferences, Conference 7
What Demons Can and Cannot Know of Our Thoughts
No one doubts that unclean spirits can influence the character of our thoughts. But they do it by working on them from outside, through things the senses can perceive: from our inclinations, or from our words, and from the likings they see we are especially given to. But they cannot possibly come near the thoughts that have not yet come out from the inmost depths of the soul. Even the thoughts they suggest, and whether these are actually embraced or embraced only in a way, they find out not from the nature of the soul itself, that is, from that inner inclination hidden, so to speak, in its very marrow, but from movements and signs given by the outward man. For example, when they suggest gluttony, if they have seen a monk lift his eyes anxiously to the window or to the sun, or ask eagerly what time it is, they know that he has let in the feeling of greed. If, when they suggest sexual immorality, they find him calmly giving way to the attack of lust, or see him stirred in body, or at least not groaning as he ought under the lewdness of an impure suggestion, they know that the dart of lust is already fixed in his very soul. If they stir up incitements to grief, or anger, or rage, they can tell whether these have taken root in the heart from the movements of the body and its visible disturbances: when, for instance, they have noticed him groaning silently, or panting with indignation, or changing color. In this way they cunningly discover the fault he is given over to. For they know that each of us is enticed in a regular way by that fault to whose incitement, as they see from a kind of assenting movement of the body, he has given his consent and agreement. And it is no wonder that these powers of the air discover this, when we see that even clever men can often discover the state of the inner man from his manner, his look and his outward bearing. How much more surely, then, can it be discovered by those who, being of a spiritual nature, are certainly far more subtle and clever than men.