It is very possible that you may not often have thought of, or clearly defined to yourselves, this destructive or deadly character of some elements of science. You may indeed have recognized with Pope that a little knowledge was dangerous, and you have therefore striven to drink deep; you may have recognized with Bacon, that knowledge might partially become venomous; and you may have sought, in modesty and sincerity, antidote to the inflating poison. But that there is a ruling spirit or σοφίa, under whose authority you are placed, to determine for you, first the choice, and then the use of all knowledge whatsoever; and that if you do not appeal to that ruler, much more if you disobey her, all science becomes to you ruinous in proportion to its accumulation, and as a net to your soul, fatal in proportion to the fineness of its thread,--this, I imagine, few of you, in the zeal of learning, have suspected, and fewer still have pressed their suspicion so far as to recognize or believe. 21. You must have nearly all heard of, many must have seen, the singular paintings; some also may have read the poems, of William Blake. The impression that his drawings once made is fast, and justly, fading away, though they are not without noble merit. But his poems have much more than merit; they are written with absolute sincerity, with infinite tenderness, and, though in the manner of them diseased and wild, are in verity the words of a great and wise mind, disturbed, but not deceived, by its sickness; nay, partly exalted by it, and sometimes giving forth in fiery aphorism some of the most precious words of existing literature. One of these passages I will ask you to remember; it will often be serviceable to you-- "Doth the Eagle know what is in the pit, Or wilt thou go ask the Mole?" It would be impossible to express to you in briefer terms the great truth that there is a different kind of knowledge good for every different creature, and that the glory of the higher creatures is in ignorance of what is known to the lower. 22. And, above all, this is true of man; for every other creature is compelled by its instinct to learn its own appointed lesson, and must centralize its perception in its own being. But man has the choice of stooping in science beneath himself, and striving in science beyond himself; and the "Know thyself" is, for him, not a law to which he must in peace submit; but a precept which of all others is the most painful to understand, and the most difficult to fulfil. Most painful to understand, and humiliating; and this alike, whether it be held to refer to the knowledge beneath us, or above. For, singularly enough, men are always most conceited of the meanest science:-- "Doth the Eagle know what is in the pit, Or wilt thou go ask the Mole?" It is just those who grope with the mole, and cling with the bat, who are vainest of their sight and of their wings.