Each group, engaged in a common task, it may be in the study of a part of nature, is ideally bound and obliged by a common language, and special standards of truth and reality for its own. Such a group of ideas is what Bacon would have called a scientific fetich or _idolum theatri_. A scientific _idolum_ is a traditional belief or dogma as to principles, values, and methods, which has so thoroughly pervaded the minds of those engaged in a branch of inquiry, that they no longer recognise its hypothetical character,—its relation of means to the main end of their function. Such a collected and united theory of reality (it is what Hegel has designated the Idea) is what is understood by a natural metaphysic. It has nothing necessarily to do with a supersensible or a supernatural, if these words mean a ghostly, materialised, but super-finely-materialised nature, above and beyond the present. But that there is a persistent tendency to conceive the unity and coherence, the theoretic idea of reality, in this pseudo-sensuous (i.e. super-sensuous) form, is of course a well-known fact. For the present, however, this aberration—this idol of the tribe—may be left out of sight. By a metaphysic or fundamental philosophy, is, in the present instance, meant a system of first principles—a secular and cosmic creed: a belief in ends and values, a belief in truth—again premising that the system in question is, for most, a rudely organised and almost inarticulate mass of belief and hope, conviction and impression. It is, in short, a _natural_ metaphysic: a metaphysic, that is, which has but an imperfect coherence, which imperfectly realises both its nature and its limits. In certain parts, however, it is more and better than this crude background of belief. Each science—or at least every group of sciences—has a more definite system or aggregate of first principles, axioms, and conceptions belonging to it. It has, that is,—and here in a much distincter way—its special standard of reality, its peculiar forms of conceiving things, its distinctions between the actual and the apparent, &c. Here again it will probably be found that the scientific specialist is hardly conscious that these are principles and concepts: on the contrary, they will be supposed self-evident and ultimate facts, foundations of being. Instead of being treated as modes of conception, more or less justified by their use and their results, these categories will be regarded as fundamental facts, essential conditions of all reality. Like popular thought in its ingrained categories, the specialist cannot understand the possibility of any limitation to his radical ideas of reality. To him they are not hypotheses, but principles. The scientific specialist may be as convinced of the universal application of his peculiar categories, as the Chinese or the Eskimo that his standards are natural and final.