The Cloud of Unknowing, ed. by Evelyn Underhill, [1922], at sacred-texts.com
How they be deceived that follow the fervour of spirit in condemning of some without discretion.
SOME men the fiend will deceive on this manner. Full wonderfully he will enflame their brains to maintain God’s law, and to destroy sin in all other men. He will never tempt them with a thing that is openly evil; he maketh them like busy prelates watching over all the degrees of Christian men’s living, as an abbot over his monks. ALL men will they reprove of their defaults, right as they had cure of their souls: and yet they think that they do not else for God, unless they tell them their defaults that they see. And they say that they be stirred p. 249 thereto by the fire of charity, and of God’s love in their hearts: and truly they lie, for it is with the fire of hell, welling in their brains and in their imagination.
That this is sooth, it seemeth by this that followeth. The devil is a spirit, and of his own nature he hath no body, more than hath an angel. But yet nevertheless what time that he or an angel shall take any body by leave of God, to make any ministration to any man in this life; according as the work is that he shall minister, thereafter in likeness is the quality of his body in some part. Ensample of this we have in Holy Writ. As oft as any angel was sent in body in the Old Testament and in the New also, evermore it was shewed, either by his name or by some instrument or quality of his body, what his matter or his message was in spirit. On the same manner it fareth of the fiend. For when he appeareth in body, he figureth in some quality of his body what his servants be in spirit. p. 250 Ensample of this may be seen in one instead of all these other. For as I have conceived by some disciples of necromancy, the which have it in science for to make advocation of wicked spirits, and by some unto whom the fiend hath appeared in bodily likeness; that in what bodily likeness the fiend appeareth, evermore he hath but one nostril, and that is great and wide, and he will gladly cast it up that a man may see in thereat to his brain up in his head. The which brain is nought else but the fire of hell, for the fiend may have none other brain; and if he might make a man look in thereto, he wants no better. For at that looking, he should lose his wits for ever. But a perfect prentice of necromancy knoweth this well enough, and can well ordain therefore, so that he provoke him not.
Therefore it is that I say, and have said, that evermore when the devil taketh any body, he figureth in some p. 251 quality of his body what his servants be in spirit. For he enflameth so the imagination of his contemplatives with the fire of hell, that suddenly without discretion they shoot out their curious conceits, and without any advisement they will take upon them to blame other men’s defaults over soon: and this is because they have but one nostril ghostly. For that division that is in a man’s nose bodily, and the which departeth the one nostril from the tother, betokeneth that a man should have discretion ghostly; and can dissever the good from the evil, and the evil from the worse, and the good from the better, ere that he gave any full doom of anything that he heard or saw done or spoken about him. And by a man’s brain is ghostly understood imagination; for by nature it dwelleth and worketh in the head. p. 252