Whatever special branch of critical scholarship a man may choose, he ought to be gifted with prudence, an exceptionally powerful attention and will, and, moreover, to combine a speculative turn of mind with complete disinterestedness and little taste for action; for he must make up his mind to work for distant and uncertain results, and, in nearly every case, for the benefit of others. For textual criticism and the investigation of sources, it is, moreover, very useful to have the puzzle-solving instinct--that is, a nimble, ingenious mind, fertile in hypotheses, prompt to seize and even to guess the relations of things. For tasks of description and compilation (the preparation of inventories and catalogues, _corpus_ and _regesta_-making) it is absolutely necessary to possess the collector's instinct, together with an exceptional appetite for work, and the qualities of order, industry, and perseverance.[116] These are the aptitudes required. The labours of external criticism are so distasteful to those who lack these aptitudes, and the results obtained are, in their case, so small in comparison with the time expended, that it is impossible for a man to make too sure of his vocation before entering upon a career of critical scholarship. It is pitiful to see those who, for want of a wise word spoken in due season, lose their way and vainly exhaust themselves in such a career, especially when they have good reason for believing that they might have employed their talents to better advantage in other directions.[117] II. As critical and preparatory tasks are remarkably well suited to the temperament of a very large number of Germans, and as the activity of German erudition during the present century has been enormous, it is to Germany that we must go for the best cases of those mental deformations which are produced, in the long run, by the habitual practice of external criticism. Hardly a year passes but complaints are heard, in and about the German universities, of the ill effects produced on scholars by the tasks of criticism.