Having made clear, by means of these examples, the character of concepts and of fictional concepts, we are prepared to solve the question as to whether the second are legitimate or illegitimate products, and if they merit the reproach which seems to attach to their name. And certainly, a view which has had and still has force does not hesitate to consider those fictions as nothing but _erroneous concepts,_ and declares a war of extermination against them, in the name of rigorous thought and of truth. If it follows from what we have said, that the cat or the house or the rose are not concepts, and that the geometrical triangle or free motion are not so either, the conclusion seems inevitable that we must free ourselves from these errors or misconceptions, and affirm that there is neither the cat nor the rose nor the house, but a reality all compact (although it is continuously changing) which develops and is new at every instant; nor is there either the triangle or free motion, but the eternal forms of this reality, which cannot be abstracted and fixed by themselves, and deprived of the conditions which are an integral part of them. But a single fact suffices to invalidate this conclusion and to confute the premiss upon which it rests, that conceptual fictions are erroneous concepts. An error once discovered cannot reappear, at least until the discovery is forgotten, and there is a falling back into the conditions of mental obscurity similar to those antecedent to the discovery. When, for example, the position has been attained that morality is not a phenomenon of egoism and that it has value in itself, or one has become certain that Hannibal was ignorant of the disaster that befell his brother Hasdrubal on the Metaurus, it is impossible to continue believing that morality is egoism, or that Hannibal has been informed of the arrival of Hasdrubal and had voluntarily allowed him to be surprised by the two Consuls. But with conceptual fictions similar to those in the example the case is otherwise. Even when we are persuaded that the triangle and free motion correspond to nothing real, and that the rose, the cat, and the house have nothing precise and universal in them, we must yet continue to make use of the fictions of triangles, of free motion; of houses, cats, and roses. We can criticise them, and we cannot renounce them; therefore, it is not true that they are, at least altogether and in every sense, errors. [Sidenote: _or imperfect concepts preparatory to perfect concepts._]