Others, who did not venture to use the idea of Deity quite so naïvely as Agassiz in zoology and botany, conceived a “law of development” within life itself. It was a time when belief in a “vital force” was universal. Living things had their peculiar force, which was not found in lifeless things. The life-principle might be at work in the law of development. It would raise living things higher and higher in the succeeding geological epochs. It was a vague theory, though it purported to cover not only the fact but the machinery of development. In the course of ages it brought about the appearance of new species. Those who held this idea of an immanent law of evolution rejected the older notion of a personal Deity, putting in an appearance suddenly at the beginning of the secondary period and creating the ichthyosauri “out of nothing.” They looked upon Cuvier’s catastrophes, to which Agassiz still clung, with a touch of Lyell’s scepticism. The “law of evolution” had been the _deus ex machina_ of the long procession of life-forms. One day a fish ceased to give birth to little fishes in the manner of its parents. The “law of evolution” was at work in its ova, and suddenly little ichthyosauri were developed from them. Thus, again, a lizard was believed to have engendered young mammals one day. One student would hold that the transition was quite abrupt in this sense. Another would think it more gradual, and approach the idea of a slow transformation of a fish into a lizard, and a lizard into a mammal, or a tree-fern into a palm-fern, and this into a true palm. At the bottom they were all agreed that the whole inner law of evolution had nothing whatever in common with the other laws of nature and was not subordinate to them. They did not hold an evolution in harmony with the great mechanism of natural laws. Their principle got astride of natural laws at certain points, like a little man, and turned them in this or that direction. Very little philosophic reflection was needed to show that they had merely replaced the Creator with a word. The older Dualism remained. On one side was the raw material of the world with the ordinary natural laws; on the other side a lord and master, the law of evolution, playing with the laws as it pleased, and moulding the material into new life-forms in an advancing series. It is true that they no longer pictured to themselves a venerable being with a white beard creating the ichthyosauri, but the finger of God remained in the law of evolution, attenuated into a special and spectral form. The God that acted from without was banished, but the “impulse from within,” reduced to a mere skeleton in substance, was put upon the throne.