It is almost inconceivable that an educated, well-balanced mind should never dwell on those immensities still unexplored, and the innumerable enigmas still unsolved or insoluble, and content itself with lingering over those comparatively insignificant truths which science so far has revealed. To what an extent a man remains satisfied with quasi-explanations of scientific research depends on the strength of his imagination. It is pardonable if alienists should look upon imagination as a doubtful blessing; but though it may appear a dangerous gift in their patients, there can be little doubt that it is an indispensable attribute to a well-equipped mind. It is the mental faculty which most distinguishes man from the animals—the one on which he could with the greatest appearance of legitimacy base his claim to divine origin. Dogs may dream and horses may see ghosts, but their hallucinations are vastly different from the imagination of man, which allows him to receive and retain almost any number of presentations, to elaborate them into new combinations, thus reconstructing pictures of the past and daring conceptions of the future, capable of easy realization. A powerful imagination is essential not only to the poet and the artist, but to the engineer, the mechanician, the statesman,—in fact, to all who set themselves a practical task or a distinct ideal. It is the imaginative strength of the scientist which renders him a pioneer and a discoverer, and without it he is to his science what the performer of music who cannot compose is to music. From everyday experience we are justified in believing that the cramming of the memory, much reading for examinations or other purposes, and a developed habit of relying on authorities tend to weaken the imagination in a man. This seems to be confirmed by the theory of psychologists: that desuetude of a faculty tends to its decay; and might well be the explanation of the often-confirmed fact that great discoverers and inventors have seldom emerged from the ranks of the omnivorous readers of the universities. In the same manner we may explain what we have before called the scientific superstition discernible in so many scientists. The more they are satisfied with their systems, the more they take nomenclature and classification for adequate explanation, the less they are attracted by the spheres into which science has not penetrated or cannot penetrate. There is this similarity between the scientifically superstitious and the theologically superstitious—that they both believe that they have explained all, and they thereby place themselves beyond the possibility of being right; for the mass of unexpected facts revealed by science, eclipsing as they do the wildest flight of the imagination, renders it possible for any man to be right in his speculations on the secrets of the universe save those men who say that they know all.