§ 5. We can now see some of the reasons which make the science of Metaphysics a peculiarly difficult branch of study. It is difficult, in the first place, from the very simplicity and generality of its problems. There is a general conviction that every science, if it is to be anything more than a body of disputes about mere words, must deal with some definite subject-matter, and it is not easy to say precisely _what_ is the subject dealt with by the metaphysician. In a certain sense this difficulty can only be met by admitting it; it is true, as we have already seen, that Metaphysics deals in some way with everything; thus it is quite right to say that you cannot specify any particular class of objects as its exclusive subject-matter. This must not, however, be understood to mean that Metaphysics is another name for the whole body of the sciences. What it does mean is that precisely because the distinction between the real and the apparent affects every department of our knowledge and enters into every one of the special sciences, the general problem as to the meaning of this distinction and the principle on which it rests cannot be dealt with by any one special science, but must form the subject of an independent inquiry. The parallel with Logic may perhaps help to make this point clearer. It is just because the principles of reasoning and the rules of evidence are, in the last resort, the same for all the sciences, that they have to be made themselves the subject of a separate investigation. Logic, like Metaphysics, deals with everything, not in the sense of being another name for the whole of our knowledge, but in the sense that it, unlike the special sciences, attacks a problem which confronts us in every exercise of our thought. The question of the difference between the two sciences will be discussed in a later section of this chapter. There are two other minor sources of difficulty, arising out of the universality of the metaphysical problem, which ought perhaps to be mentioned, as they present a serious obstacle to the study of Metaphysics by minds of a certain stamp. In Metaphysics we have no such helps to the imagination as the figures and diagrams which are so useful in many branches of Mathematics; and again, we are, by the nature of the problem, entirely cut off from the aid of physical experiment. All our results have to be reached by the unassisted efforts of thought in the strictest sense of the word, that is, by the rigid and systematic mental analysis of conceptions. Thus Metaphysics stands alone among the sciences, or alone with Logic, in the demand it makes on the student’s capacity for sheer hard continuous thought This may help to explain why men who are capable of excellent work in the domain of mathematical or experimental science sometimes prove incompetent in Metaphysics; and again, why eminent metaphysical ability does not always make its possessor a sound judge of the results and methods of the other sciences.