A further question still remains: _If_ the revelation was by vision, that circumstance affords of itself a satisfactory reason why the description should be _optical_; and, on the other hand, since the description is decidedly _optical_, the presumption is of course strong that the revelation was by vision. But why, it may be asked, by vision? Can the presumption be yet further strengthened by showing that this visual mode or form was preferable to any other? Can there be a reason, in fine, assigned _for_ the _reason_,--for that revelation by vision which accounts for the optical character of the description? The question is a difficult one; but I think there can. There seems to be a peculiar fitness in a revelation made by vision, for conveying an account of creation to various tribes and peoples of various degrees of acquirement, and throughout a long course of ages in which the knowledge of the heavenly bodies or of the earth's history, that is, the sciences of astronomy and geology, did not at first exist, but in which ultimately they came to be studied and known. We must recognize such a mode as equally fitted for the earlier and the more modern times,--for the ages anterior to the rise of science, and the ages posterior to its rise. The prophet, by describing what he had actually seen in language fitted to the ideas of his time, would shock no previously existing prejudice that had been founded on the apparent evidence of the senses; he could as safely describe the moon as the second great light of creation, as he could the sun as its first great light, and both, too, as equally subordinate to the planet which we inhabit. On the other hand, an enlightened age, when it had come to discover this key to the description, would find it _optically_ true in all its details. But how differently would not a revelation have fared, in at least the earlier time, that was strictly scientific in its details,--a revelation, for instance, of the great truth demonstrated by Galileo, that the sun rests in the centre of the heavens, while the apparently immoveable earth sweeps with giddy velocity around it; or of the great truth demonstrated by Newton, that our ponderous planet is kept from falling off into empty space by the operation of the same law that impels a descending pebble towards the ground! A great miracle wrought in proof of the truth of the revelation might serve to enforce the belief of it on the generation to whom it had been given; but the generations that followed, to whom the miracle would exist as a piece of mere testimony, would credit, in preference, the apparently surer evidence of their senses, and become unbelievers. They would act, all unwittingly, on the principle of Hume's famous argument, and prefer to rest rather on their own _experience_ of the great phenomena of nature, than on the doubtful testimony of their ancestors, reduced in the lapse of ages to a dim, attenuated tradition.