In speaking of an evolution theory, in distinction from the descent theory, we mean, as is evident from the first part of our work, that way and mode of {264} constructing the doctrine of the descent of species which permit this descent to take place, not by the leaps of a metamorphosis of germs, but by transitions so imperceptably small that the difference of two generations which lie in the same line of descent, is never greater than those differences which always take place between parents and children of the same species--transitions so gradual that only the continuation of these individual changes in a single direction produces an increase and, finally and gradually, the new species. The treatment of the question as to what position this _evolution theory_ takes regarding theism, is even more simple than answering the question as to the position of the descent idea in reference to theism. For now we have no longer to discuss the different possibilities of a development, as heretofore we have discussed those of a descent, but only the idea of a gradual development or of an evolution in general. Of such possibilities, it is true, we find several. In the first place, we can look for the inciting principle of the development of species either in the interior of organisms, or we can see it approaching the latter from without. The only scientific system which has made any attempt at mentioning and elaborating the inciting principle of development is that of Darwin; a system that chooses the second of the alternatives just stated and sees the essential principle that makes the transmission of individuals a progress beyond one species, approaching the individuals from without. But while we shall have to treat of this specific Darwinian theory--the selection theory--still more in detail in the following section, we shall also there have to point, out {265} everything that theism has to say in reference to a principle of development which approaches the organisms from without. Another possible explanation of the origin of species through development is to be found in the fact that we look for the inciting principle of development in the interior of organisms. This is done, so far as we know, by all those scientists who, although inclined to an evolution theory, are adversaries of the selection theory; but none of them claim to have found the inciting agencies of development. Thus, as in the preceding section, we are again referred only to the wholly abstract possibility of conceiving these inciting agencies either as coming into existence anew in the organism with each smallest individual modification which leads to a development of the species, or as being before present in the organisms, but still latent, and only coming into activity when they are set free. But the question whether theism could accept the one or the other possibility had to be treated of in the preceding section, and was there answered in the affirmative.