Other causes contribute to produce the natural and intrinsic concurrence of the several stages of myth which are found existing together in the life of a people. Such, for example, is the conquest effected by a more civilized nation over another race, inferior by nature or retarded by other circumstances. The mythical ideas of the conquered people remain, and are even diffused through the lower classes of the conquering race; or they are ingrafted by a synthetic and assimilating process, so as to modify other mythical and religious beliefs. This compound of various stages and various beliefs also occurs through the moral and intellectual diffusion of dogma, without the acquisition of really new matter. Manifest proofs of these various stages of myth, co-existent together, may be traced in the development of the Vedic ideas among the earlier aboriginal nations, and conversely; as in the case of the Aztecs and Incas in Mexico and Peru, whose earlier beliefs were mixed with those of their conquerors. The same thing may be observed in the development of Judaism during the Babylonish captivity, in the biblical and messianic doctrines which were grafted on pagan beliefs, and in the teaching of Islam, as it was adopted in the East and among the black races of Africa. We must make allowance for these extrinsic accidents if we are to describe correctly the natural course and logical evolution of myth. Even with respect to the special evolution of myth in a separate people, unmixed with others, while it is normal in what may be termed its general form and categorical phases, yet like all natural objects and phenomena, and much more in all which concerns the human mind, there are variations in its forms, and it attains its ends by many ways. If we take a wider view of the general and reciprocal influences of ethnic myths; as respects the historic results of mythologies, we shall see that if every race evolved its sphere of myth in accordance with the canons laid down by us, their effect upon each other would work together for a common result more quickly than when each is taken apart. The reader must allow me to make my meaning clear by the following passage from my work on the "Dottrina razionale del Progresso," which I published in 1863, in the "Politecnico," Milan, on the fusion of the monotheistic conception of the Semitic race with the beliefs of Greece and Rome at the dawn of Christianity:--