cause which was non-material, that is, spiritual and final, or at least unknown--and so on. When it is demonstrated of a concept that it has been suggested by contingent facts, by this very fact we eliminate it from the series of true concepts, and substitute for it another concept, which is given as truly universal. Or again, we suppress it without substituting another for it, that is to say, we reduce the number of true and proper concepts. Such a reduction is a progress of thought, but it is a progress which can never be extended to the abolition of all concepts, because one, at least, will always remain ineliminable; that of thought, which thinks the abolition; and this concept will be ultra- and omnirepresentative. [Sidenote: _Conceptual fictions as representative without universality,_] Fictional concepts or conceptual fictions are something altogether different. In these, either the content is furnished by a group of representations, even by a single representation, so that they are not ultrarepresentative; or there is no representable content, so that they are not omnirepresentative. Examples of the first type are afforded by the concepts of _house, cat, rose_; of the second, those of _triangle,_ or of _free motion._ If we think of the house, we refer to an artificial structure of stone or masonry or wood, or iron or straw, where beings, whom we call men, are wont to abide for some hours, or for entire days and entire years. Now, however great may be the number of objects denoted by that concept, it is always a finite number; there was a time when man did not exist, when, therefore, neither did his house; and there was another time when man existed without his house, living in caverns and under the open sky. Of course, undoubtedly, we shall be able to extend the concept of house, so as to include also the places inhabited by animals; but it will never be possible to follow with absolute clearness the distinction between artificial and natural (the act of inhabiting itself makes the place more or less artificial, by changing, for instance, the temperature); or between the animals which are inhabitants and the non-animals, which nevertheless are inhabitants, such as plants, which, as well as animals, often seek a roof; admitting that certain plants and animals have other plants and animals as their houses. Hence, in view of the impossibility of a clear and universal distinctive character, it is advisable to have recourse at once to enumeration and to give the name house to certain particular objects, which, however numerous they are, are also finite in number, and which, with the enumeration complete, or capable of completion, exclude other objects from themselves. If it is desired to prevent this exclusion, no other course remains than that of understanding by _house_ any mode of life between different beings; but in that case, the conceptual fiction becomes changed into a universal,