When the problems involved in mental telegraphy come to be generally viewed under the guidance of a sound logic, the outlook will be hopeful that the whole domain will gradually acquire definite order; and that its devotees, after appreciating the statistical regularity of the phenomena, will come to the conclusion that much of the energy and ability now expended in a search for the explanation of complex and necessarily indefinite individual cases, is on the whole unprofitable. With an infinite time and an infinite capacity it might be profitable to study all things; but, at present, sanity consists in the maintenance of a proper perspective of the relative importance of the affairs of the intellectual and the practical life. It may be that the man who puzzles day and night over some trivial mystery expends as much brain energy as a great intellectual benefactor of mankind; but the world does not equally cherish the two. III It becomes important in the further consideration of coincidences to emphasize the great opportunity presented in their description for error, for defective observation, for neglect of details, for exaggeration of the degree of correspondence; and equally demonstrable is the slight amount of such error or mal-observation that is all-sufficient to convert a plain fact into a mystery. Consider the disfigurement that a simple tale undergoes as it passes from mouth to mouth; the forgetfulness of important details and the introduction of imaginary ones, exhibited upon the witness stand; the almost universal tendency to substitute inferences from sensations and observations for the actual occurrences; and add to these the striking results of experimental inquiry in this direction--for example, the divergences between the accounts of sleight-of-hand performances or spiritualistic séances and what really occurred--and it becomes less difficult to understand why we so often fail to apply general principles to individual cases. The cases cannot be explained as they are recorded, because as recorded they do not furnish the essential points upon which the explanation hinges. The narrator may be confident that the points of the story are correctly observed, that all the details are given; and yet this feeling of confidence is by no means to be trusted. It is quite possible that the points that would shed most light on the problem are too trivial to attract attention; a slightly imperfect connection as effectively breaks the circuit and cuts off the possibility of illumination as a more serious disturbance. After the explanation is given or the gap supplied or the break discovered, we often wonder how we could have failed to detect the source of the mystery; but before we know what to observe and what to record and what to be on our guard against, the possibility of error is extremely great, far greater than most of us would be willing to make allowance for; and the