So extensive is the field of human knowledge, so many and wide apart are the spots at which ground has been broken, and so evident is the necessity for men to be special in their studies if they would be thoroughly masters of their subjects, that there is no little danger lest workers in one department may be unappreciated by, if not actually unknown to, those who are employed in another part. Any one who will give his attention to the matter may observe examples of lines of investigation, which have really close relations, and the results of which might be of mutual aid, running side by side, like parallel lines, without meeting. Accordingly, M. Comte was of opinion that there was needed a new order of scientific men, whose function it should be to bring together and co-ordinate the results of the different workers; and it is plain that such an organisation must be effected somehow. But great mischief would of a certainty result from men specially undertaking this work: unless they are thoroughly and practically grounded in some science, unless they have plodded in patient and tedious investigation, they are almost sure to go astray into vain and seductive speculations, which are never definite enough to be useful, are often enticing enough to be mischievous. If a valuable idea is perchance hit upon, it is potential rather than real, as a statue is potential in a block of marble, though it has yet to be hewn out; it is so shrouded in theoretical haze, and so much wanting in exactness, that it is of no value until the patient work of the practical men has defined it, put it in its proper place, and so to speak guaranteed its worth. Even Goethe, exceptionally powerful as his mind was, and much as he worked, owed his scientific troubles and his scientific errors to a want of practical knowledge. Those who have not had a scientific training must lack the scientific imagination.