Guide for the Perplexed, by Moses Maimonides, Friedländer tr. , at sacred-texts.com
EVERY man possesses a certain amount of courage, otherwise he would not stir to remove anything that might injure him. This psychical force seems to me analogous to the physical force of repulsion. Energy varies like all other forces, being great in one case and small in another. There are, therefore, people who attack a lion, whilst others run away at the sight of a mouse. One attacks a whole army and fights, another is frightened and terrified by the threat of a woman. This courage requires that there be in a man's constitution a certain disposition for it. If man, in accordance with a certain view, employs it more frequently, it develops and increases, but, on the other hand, if it is employed, in accordance with the opposite view, more rarely, it will diminish. From our own youth we remember that there are different degrees of energy among boys.
The same is the case with the intuitive faculty; all possess it, but in different degrees. Man's intuitive power is especially strong in things which he has well comprehended, and in which his mind is much engaged. Thus you may yourself guess correctly that a certain person said or did a certain thing in a certain matter. Some persons are so strong and sound in their imagination and intuitive faculty that, when they assume a thing to be in existence, the reality either entirely or partly confirms their assumption. Although the causes of this assumption are numerous, and include many preceding, succeeding, and present circumstances, by means of the intuitive faculty the intellect can pass over all these causes, and draw inferences from them very quickly, almost instantaneously. This same faculty enables some persons to foretell important coming events. The prophets must have had these two forces, courage and intuition, highly developed, and these were still more strengthened when they were under the influence of the Active Intellect. Their courage was so great that, e.g., Moses, with only a staff in his hand, dared to address a great king in his desire to deliver a nation from his service. He was not frightened or terrified, because he had been told, "I will be with thee" (Exod. iii. 12). The prophets have not all the same degree of courage, but none of them have been entirely without it. Thus Jeremiah is told: "Be not afraid of them," etc. (Jer. i. 8), and Ezekiel is exhorted, "Do not fear them or their word" (Ezek. ii. 6). In the same manner, you find that all prophets possessed great courage. Again, through the excellence of their intuitive faculty, they could quickly foretell the future, but this excellence, as is well known, likewise admits of different degrees.
The true prophets undoubtedly conceive ideas that result from premisses which human reason could not comprehend by itself; thus they tell things which men could not tell by reason and ordinary imagination alone; for [the action of the prophets' mental capacities is influenced by] the same agent that causes the perfection of the imaginative faculty, and that enables the prophet thereby to foretell a future event with such clearness as if it was a thing already perceived with the senses, and only through them conveyed to his imagination. This agent perfects the prophet's mind, and influences it in such a manner that he conceives ideas which are confirmed by reality, and are so clear to him as if he deduced them by means of syllogisms.
This should be the belief of all who choose to accept the truth. For [all things are in a certain relation to each other, and] what is noticed in one thing may be used as evidence for the existence of certain properties in another, and the knowledge of one thing leads us to the knowledge of other things But [what we said of the extraordinary powers of our imaginative faculty] applies with special force to our intellect, which is directly influenced by the Active Intellect, and caused by it to pass from potentiality to actuality. It is through the intellect that the influence reaches the imaginative faculty. How then could the latter be so perfect as to be able to represent things not previously perceived by the senses, if the same degree of perfection were withheld from the intellect, and the latter could not comprehend things otherwise than in the usual manner, namely, by means of premiss, conclusion, and inference? This is the true characteristic of prophecy, and of the disciplines to which the preparation for prophecy must exclusively be devoted. I spoke here of true prophets in order to exclude the third class, namely, those persons whose logical faculties are not fully developed, and who do not possess any wisdom, but are only endowed with imaginative and inventive powers. It may be that things perceived by these persons are nothing but ideas which they had before, and of which impressions were left in their imaginations together with those of other things; but whilst the impressions of other images are effaced and have disappeared, certain images alone remain, are seen and considered as new and objective, coming from without. The process is analogous to the following case: A person has with him in the house a thousand living individuals; all except one of them leave the house: when the person finds himself alone with that individual, he imagines that the latter has entered the house now, contrary to the fact that he has only not left the house. This is one of the many phenomena open to gross interpretations and dangerous errors, and many of those who believed that they were wise perished thereby.
There were, therefore, men who supported their opinion by a dream which they had, thinking that the vision during sleep was independent of what they had previously believed or heard when awake. Persons whose mental capacities are not fully developed, and who have not attained intellectual perfection, must not take any notice of these [dreams]. Those who reach that perfection may, through the influence of the divine intellect, obtain knowledge independent of that possessed by them when awake. They are true prophets, as is distinctly stated in Scripture, ve-nabi lebab ḥokmah (Ps. xc. 12), "And the true prophet possesseth a heart of wisdom." This must likewise he noticed.