Being provided with a conviction of what it is that he wants to know, the traveller must be furthermore furnished with the means of gaining the knowledge he wants. When he was a child, he was probably taught that eyes, ears, and understanding are all-sufficient to gain for him as much knowledge as he will have time to acquire; but his self-education has been a poor one, if he has not become convinced that something more is needful--the enlightenment and discipline of the understanding, as well as its immediate use. It is not enough for a traveller to have an active understanding, equal to an accurate perception of individual facts in themselves; he must also be in possession of principles which may serve as a rallying point for his observations, and without which he cannot determine their bearings, or be secure of putting a right interpretation upon them. A traveller may do better without eyes, or without ears, than without such principles, as there is evidence to prove. Holman, the blind traveller, gains a wonderful amount of information, though he is shut out from the evidence yielded by the human countenance, by way-side groups, by the aspect of cities, and the varying phenomena of country regions. In his motto, he indicates something of his method. "Sightless to see, and judge thro' judgment's eyes, To make four senses do the work of five, To arm the mind for hopeful enterprise, Are lights to him who doth in darkness live." In order to "judge through judgment's eyes," those eyes must be made strong and clear; and a traveller may gain more without the bodily organ than with an untrained understanding. The case of the Deaf Traveller[A] leads us to say the same about the other great avenue of knowledge. His writings prove, to all who are acquainted with them, that, though to a great degree deprived of that inestimable commentary upon perceived facts--human discourse--the Deaf Traveller is able to furnish us with more knowledge of foreign people than Fine-Ear himself could have done without the accompaniments of analytical power and concentrative thought. All senses, and intellectual powers, and good habits, may be considered essential to a perfect observation of morals and manners; but almost any one might be better spared than a provision of principles which may serve as a rallying point and a test of facts. The blind and the deaf travellers must suffer under a deprivation or deficiency of certain classes of facts. The condition of the unphilosophical traveller is much worse. It is a chance whether he puts a right interpretation on any of the facts he perceives.