Reply Obj. 1: The first principle of the imagination is from the sense in act. For we cannot imagine what we have never perceived by the senses, either wholly or partly; as a man born blind cannot imagine color. Sometimes, however, the imagination is informed in such a way that the act of the imaginative movement arises from the impressions preserved within.
Reply Obj. 2: An angel changes the imagination, not indeed by the impression of an imaginative form in no way previously received from the senses (for he cannot make a man born blind imagine color), but by local movement of the spirits and humors, as above explained.
Reply Obj. 3: The commingling of the angelic spirit with the human imagination is not a mingling of essences, but by reason of an effect which he produces in the imagination in the way above stated; so that he shows man what he [the angel] knows, but not in the way he knows.
Reply Obj. 4: An angel causing an imaginative vision, sometimes enlightens the intellect at the same time, so that it knows what these images signify; and then there is no deception. But sometimes by the angelic operation the similitudes of things only appear in the imagination; but neither then is deception caused by the angel, but by the defect in the intellect to whom such things appear. Thus neither was Christ a cause of deception when He spoke many things to the people in parables, which He did not explain to them. _______________________
FOURTH ARTICLE [I, Q. 111, Art. 4]
Whether an Angel Can Change the Human Senses?
Objection 1: It seems that an angel cannot change the human senses. For the sensitive operation is a vital operation. But such an operation does not come from an extrinsic principle. Therefore the sensitive operation cannot be caused by an angel.
Obj. 2: Further, the sensitive operation is nobler than the nutritive. But the angel cannot change the nutritive power, nor other natural forms. Therefore neither can he change the sensitive power.
Obj. 3: Further, the senses are naturally moved by the sensible objects. But an angel cannot change the order of nature (Q. 110, A. 4). Therefore an angel cannot change the senses; but these are changed always by the sensible object.
On the contrary, The angels who overturned Sodom, "struck the people of Sodom with blindness or aorasia, so that they could not find the door" (Gen. 19:11). [*It is worth noting that these are the only two passages in the Greek version where the word aorasia appears. It expresses, in fact, the effect produced on the people of Sodom—namely, dazzling (French version, "eblouissement"), which the Latin "caecitas" (blindness) does not necessarily imply.] The same is recorded of the Syrians whom Eliseus led into Samaria (4 Kings 6:18).