Well, that same need of relating our knowledge which operates here within the sphere of our knowledge itself, we shall find operating, also, outside that sphere. We feel, as we go on learning and knowing, the vast majority of mankind feel, the need of relating what we have learned and known to the sense which we have in us for conduct, to the sense which we have in us for beauty.
The prophetess Diotima explained to Socrates that love is, in fact, nothing but the desire in men that good should be for ever present to them. This primordial desire it is, I suppose—this desire in men that good should be for ever present to them—which causes in us the instinct for relating our knowledge to our sense for conduct and to our sense for beauty. At any rate, with men in general the instinct exists. Such is human nature. Such is human nature; and, in seeking to gratify the instinct, we are following the instinct of self-preservation in humanity.
Knowledges which can not be directly related to the sense for beauty, to the sense for conduct, are instrument-knowledges; they lead on to other knowledge, which can. A man who passes his life in instrument-knowledges is a specialist. They may be invaluable as instruments to something beyond, for those who have the gift thus to employ them; and they may be disciplines in themselves wherein it is useful to every one to have some schooling. But it is inconceivable that the generality of men should pass all their mental life with Greek accents or with formal logic. My friend Professor Sylvester, who holds transcendental doctrines as to the virtue of mathematics, is far away in America; and, therefore, if in the Cambridge Senate House one may say such a thing without profaneness, I will hazard the opinion that, for the majority of mankind, a little mathematics, also, goes a long way. Of course, this is quite consistent with their being of immense importance as an instrument to something else; but it is the few who have the aptitude for thus using them, not the bulk of mankind.
The natural sciences do not stand on the same footing with these instrument-knowledges. Experience shows us that the generality of men will find more interest in learning that, when a taper burns, the wax is converted into carbonic acid and water, or in learning the explanation of the phenomenon of dew, or in learning how the circulation of the blood is carried on, than they find in learning that the genetive plural of pais and pas does not take the circumflex on the termination. And one piece of natural knowledge is added to another, and others to that, and at last we come to propositions so interesting as the proposition that "our ancestor was a hairy quadruped furnished with a tail and pointed ears, probably arboreal in his habits." Or we come to propositions of such reach and importance as those which Professor Huxley brings us, when he says that the notions of our forefathers about the beginning and the end of the world were all wrong,