These are the motives of the collector, and in a sense the scientist is a collector of facts, as others collect coins, or stamps, or china, or old furniture. The impelling motives of curiosity and excellence are much the same. There are people who gather and assort clippings from the newspapers, for the mere collecting instinct of it, gather them on all sorts of subjects, with the scientist’s obscure impulse to accumulate knowledge even if they do not use it. We are too apt to associate science exclusively with the study of nature, and in this way the thought of the scientific spirit is altogether too much restricted. Its real field is as vast as that of human interests, and scientific methods and scientific purposes apply as much to philology, to history, to religion, to the general movements of human society, as to the curious consideration of animals and plants and stones and chemical elements. But if mere curiosity is to become truly scientific, it must be broadened and deepened into research. That is, the simple collection of facts must be systematized by a definite object and method. The mere garnering of one fact and another here and there, though it often has its great and singular charm, is apt to degenerate into aimlessness and futility. It must be guided and solidified by the sense of working toward some particular conclusion which will give all the facts coherence and significance. In other words, the relation of the facts must be studied, as well as the facts themselves, they must be coördinated and subordinated, till their real depth of meaning is revealed. How nicely does Darwin indicate the proportionate connection between theory and observation in the following passage: ‘_Let theory guide your observations_, but till your reputation is well established, be sparing in publishing theory. It makes persons doubt your observations.’[127] Two of the supreme elements of research are completeness and correctness. It is true that final completeness can rarely be obtained in this world, but the important thing is to aim at it, to leave no stone unturned, no nook unsearched, to gather every possible fact from every possible source, before one allows oneself to deduce positive conclusions, or conclusions that even approach positiveness. And besides the completeness, one should test one’s position from every aspect, to insure its being, so far as possible, correct. No one but the trained scientific thinker appreciates thoroughly the vast possibility of error, or is sufficiently aware how apt error is to intrude its subtle and treacherous working into the most careful investigations and the most logically buttressed theories. In one of his immensely suggestive casual phrases Darwin remarks, ‘The history of error is quite unimportant.’[128] This may be true enough as regards the abstract progress of science, but assuredly the history of error is of the highest interest to the curious student of the human mind.