What, then, is man’s proud prerogative? What the gift which has given him the world and all that therein is? The answer is in one word,—_ideation_. The last efforts of modern science can but paraphrase the words which the philosopher Locke penned nigh two centuries ago: “The having of general ideas is that which puts a perfect distinction between man and brute.” The latest American writer on the subject merely repeats this when he phrases it “the ability to think in general terms by using symbols (words) which summarise systems of association.” Let us avoid the metaphysical snares which have been spread around this simple statement. No matter about such words as “concepts,” “notions,” “apperceptions,” “abstractions,” and the like. Let us fix in mind the formula of Romanes: “Distinctively human faculty belongs with distinctively human ideation.” This, the power to form general ideas,—which are necessarily abstract,—is the one prerogative which lifts man above brute. By it he can compare what he learns and thus develop an intellectual life for comparison; to borrow the metaphor of a famous student of his kind, it is the magic wand, the diamond-hilted sword, by which man will conquer his salvation through learning the truth. We exclaim, with Pascal, “It is Thought which makes Man.” Outside of this and its developments, all that man has of soul-life is in common with the brute. Why should he be ashamed of it? What folly to pretend, as the common phrase goes, to “get rid of the brute in man”! Parental love, social instincts, fidelity, friendship, courage,—these are parts of his heritage from his four-footed ancestor. What would he become, dispossessed of them? Already, in that long alienation from his brethren which made man the one species of his genus and the one genus of his class, has he lost certain strange powers of mind which excite our special wonder when we see their manifestations in his remote relations. The chief of these is Instinct. We are all familiar with its extraordinary exhibitions in bees, ants, and higher animals, and its seeming total absence in ourselves. What can we make of it? _Instinct and Intelligence._—Throughout all nature there is an unceasing eternal conflict between the old and the new, between motion and rest, between the fixed and the variable, between the individual and the universe. This cosmic contest is reflected within the realm of animal life in the contrast between Instinct and Intelligence. Instinct is hereditary; it belongs to the species; its performance is unconscious, resulting from internal impulse; its tendency is endless repetition, not improvement; it is petrified, inherited habit. Intelligence belongs to the individual; it is neither inherited nor transmissible by blood; its tendency is toward advancement, progress. It is the source of all knowledge not purely empirical, and of all development not of chance.