Objection 1. It would seem that the prophecy which has intellective and imaginative vision is more excellent than that which is accompanied by intellective vision alone. For Augustine says (Gen. ad lit. xii, 9): "He is less a prophet, who sees in spirit nothing but the signs representative of things, by means of the images of things corporeal: he is more a prophet, who is merely endowed with the understanding of these signs; but most of all is he a prophet, who excels in both ways," and this refers to the prophet who has intellective together with imaginative vision. Therefore this kind of prophecy is more excellent.
Objection 2. Further, the greater a thing's power is, the greater the distance to which it extends. Now the prophetic light pertains chiefly to the mind, as stated above (Question 173, Article 2). Therefore apparently the prophecy that extends to the imagination is greater than that which is confined to the intellect.
Objection 3. Further, Jerome (Prol. in Lib. Reg.) distinguishes the "prophets" from the "sacred writers." Now all those whom he calls prophets (such as Isaias, Jeremias, and the like) had intellective together with imaginative vision: but not those whom he calls sacred writers, as writing by the inspiration of the Holy Ghost (such as Job, David, Solomon, and the like). Therefore it would seem more proper to call prophets those who had intellective together with imaginative vision, than those who had intellective vision alone.
Objection 4. Further, Dionysius says (Coel. Hier. i) that "it is impossible for the Divine ray to shine on us, except as screened round about by the many-colored sacred veils." Now the prophetic revelation is conveyed by the infusion of the divine ray. Therefore it seems that it cannot be without the veils of phantasms.
On the contrary, A gloss says at the beginning of the Psalter that "the most excellent manner of prophecy is when a man prophesies by the mere inspiration of the Holy Ghost, apart from any outward assistance of deed, word, vision, or dream."
I answer that, The excellence of the means is measured chiefly by the end. Now the end of prophecy is the manifestation of a truth that surpasses the faculty of man. Wherefore the more effective this manifestation is, the more excellent the prophecy. But it is evident that the manifestation of divine truth by means of the bare contemplation of the truth itself, is more effective than that which is conveyed under the similitude of corporeal things, for it approaches nearer to the heavenly vision whereby the truth is seen in God's essence. Hence it follows that the prophecy whereby a supernatural truth is seen by intellectual vision, is more excellent than that in which a supernatural truth is manifested by means of the similitudes of corporeal things in the vision of the imagination.
Moreover the prophet's mind is shown thereby to be more lofty: even as in human teaching the hearer, who is able to grasp the bare intelligible truth the master propounds, is shown to have a better understanding than one who needs to be taken by the hand and helped by means of examples taken from objects of sense. Hence it is said in commendation of David's prophecy (2 Samuel 23:3): "The strong one of Israel spoke to me," and further on (2 Samuel 23:4): "As the light of the morning, when the sun riseth, shineth in the morning without clouds."
Reply to Objection 1. When a particular supernatural truth has to be revealed by means of corporeal images, he that has both, namely the intellectual light and the imaginary vision, is more a prophet than he that has only one, because his prophecy is more perfect; and it is in this sense that Augustine speaks as quoted above. Nevertheless the prophecy in which the bare intelligible truth is revealed is greater than all.
Reply to Objection 2. The same judgment does not apply to things that are sought for their own sake, as to things sought for the sake of something else. For in things sought for their own sake, the agent's power is the more effective according as it extends to more numerous and more remote objects; even so a physician is thought more of, if he is able to heal more people, and those who are further removed from health. on the other hand, in things sought only for the sake of something else, that agent would seem to have greater power, who is able to achieve his purpose with fewer means and those nearest to hand: thus more praise is awarded the physician who is able to heal a sick person by means of fewer and more gentle remedies. Now, in the prophetic knowledge, imaginary vision is required, not for its own sake, but on account of the manifestation of the intelligible truth. Wherefore prophecy is all the more excellent according as it needs it less.
Reply to Objection 3. The fact that a particular predicate is applicable to one thing and less properly to another, does not prevent this latter from being simply better than the former: thus the knowledge of the blessed is more excellent than the knowledge of the wayfarer, although faith is more properly predicated of the latter knowledge, because faith implies an imperfection of knowledge. On like manner prophecy implies a certain obscurity, and remoteness from the intelligible truth; wherefore the name of prophet is more properly applied to those who see by imaginary vision. And yet the more excellent prophecy is that which is conveyed by intellectual vision, provided the same truth be revealed in either case. If, however, the intellectual light be divinely infused in a person, not that he may know some supernatural things, but that he may be able to judge, with the certitude of divine truth, of things that can be known by human reason, such intellectual prophecy is beneath that which is conveyed by an imaginary vision leading to a supernatural truth. It was this kind of prophecy that all those had who are included in the ranks of the prophets, who moreover were called prophets for the special reason that they exercised the prophetic calling officially. Hence they spoke as God's representatives, saying to the people: "Thus saith the Lord": but not so the authors of the "sacred writings," several of whom treated more frequently of things that can be known by human reason, not in God's name, but in their own, yet with the assistance of the Divine light withal.
Reply to Objection 4. In the present life the enlightenment by the divine ray is not altogether without any veil of phantasms, because according to his present state of life it is unnatural to man not to understand without a phantasm. Sometimes, however, it is sufficient to have phantasms abstracted in the usual way from the senses without any imaginary vision divinely vouchsafed, and thus prophetic vision is said to be without imaginary vision.
Source: Summa Theologica (New Advent)