Know that also in Natural Science there are topics which are not to be fully explained. Our Sages laid down the rule, “The Maʻaseh Bereshith must not be expounded in the presence of two.” If an author were to explain these principles in writing, it would be equal to expounding them unto thousands of men. For this reason the prophets treat these subjects in figures, and our Sages, imitating the method of Scripture, speak of them in metaphors and allegories; because there is a close affinity between these subjects and metaphysics, and indeed they form part of its mysteries. Do not imagine that these most difficult problems can be thoroughly understood by any one of us. This is not the case. At times the truth shines so brilliantly that we perceive it as clear as day. Our nature and habit then draw a veil over our perception, and we return to a darkness almost as dense as before. We are like those who, though beholding frequent flashes of lightning, still find themselves in the thickest darkness of the night. On some the lightning flashes in rapid succession, and they seem to be in continuous light, and their night is as clear as the day. This was the degree of prophetic excellence attained by (Moses) the greatest of prophets, to whom God said, “But as for thee, stand thou here by Me” (Deut. v. 31), and of whom it is written “the skin of his face shone,” etc. (Exod. xxxiv. 29). [Some perceive the prophetic flash at long intervals; this is the degree of most prophets.] By others only once during the whole night is a flash of lightning perceived. This is the case with those of whom we are informed, “They prophesied, and did not prophesy again” (Num. xi. 25). There are some to whom the flashes of lightning appear with varying intervals; others are in the condition of men, whose darkness is illumined not by lightning, but by some kind of crystal or similar stone, or other substances that possess the property of shining during the night; and to them even this small amount of light is not continuous, but now it shines and now it vanishes, as if it were “the flame of the rotating sword.” The degrees in the perfection of men vary according to these distinctions. Concerning those who never beheld the light even for one day, but walk in continual darkness, it is written, “They know not, neither will they understand; they walk on in darkness” (Ps. lxxxii. 5). Truth, in spite of all its powerful manifestations, is completely withheld from them, and the following words of Scripture may be applied to them, “And now men see not the light which is bright in the skies” (Job xxxvii. 21). They are the multitude of ordinary men; there is no need to notice them in this treatise.