_A priori_ is therefore reduced by us to the modification of organs in their physical and psychical constitution, as it has ultimately taken place in the organism by the successive evolutions of forms which have gradually become permanent, and are perpetuated by embryogenic reproduction. This reproduction is in its turn the absolute condition of psychical and organic facts, which are thus manifested as primitive facts in the new life of the individual. By this law, the psychical facts, whether elementary or complex, as they occur in the individual up to the point of their evolution, have the necessary conditions of possibility, and may therefore be termed a _priori_ with respect to the laws of evolution, and to the hereditary permanence of acts performed in the former environment of the organism at the time when they appeared. This conception of a _priori_ is, it must be admitted, very different from that of transcendental philosophers, who seek to prove either that an independent artificer has not only produced the various organic forms in their present complexity, and has specially provided the spiritual subject with its category of thought, independently of all experience; or else they assert the intrinsic existence of such forms in the spirit, from the beginning of time. In this way, as we have already said, we must not only collect the facts which abound in history and ethnology respecting the general teaching of myths, but we must also observe introspectively, and by pursuing the experimental method, the primitive and fundamental psychical facts, so as to discover the a priori conditions of the myth itself. We must ascertain, from a careful psychological examination, the absolutely primitive origin of all mythical representations, and how these are in their turn the actual historical result of the same conditions, as they existed prior to their manifestations. It must not be supposed that in this primary fact, and in these _a priori_ psychical and organic conditions, we shall find the ulterior cause of the various and manifold forms, or of the successive evolution of myths. This would be a grave mistake, equal to that of transcendentalists, who imagine that the laws which actually exist, and the order of cosmic and historic phenomena may be determined from the independent exercise of their own thoughts, although such laws and order can only be traced and discovered by experience and the observation of facts. In the _a priori_ conditions of the psychical and organic nature, and in the elementary acts which outwardly result from them, we shall only trace the origin and necessary source of myth, not the variable forms of its successive evolution.