Tyndall's statement of the scope of the theory is as follows: "Strip it naked and you stand face to face with the notion, that not only the ignoble forms of life, the animalcular and animal life, not only the more noble forms of the horse and lion, not only the exquisite mechanism of the human body, but the human mind with its emotions, intellect, will and all their phenomena, were latent in that fiery cloud." (Christianity and Positivism, p. 30.)
Dr. Lyman Abbott further defines its application to man thus: "Evolution is the doctrine that this life of man, this moral, this ethical, this spiritual nature has been developed by natural processes." (Theology of an Evolutionist.)
Herbert Spencer's celebrated definition is as follows: "Evolution is a progress from the homogeneous to the heterogeneous, from general to special, from the simple to the complex elements of life." But we deny the right to apply this definition exclusively to the theory of Evolution. Creation also proceeds on the same order, so also does manufacture or any other intelligent operation.
The clearest account of the theory is that given by Prof. Le Conte, as follows: "All things came (1) by continuous progressive changes, (2) according to certain laws, (3) by means of resident forces." (Evolution and Religious Thought.) It is the latter clause in which the real meaning of the theory lies. These "resident forces" include exterior influences such as food, climate, etc.
The theories of Evolution are as many as the respective writers. Each one has his own theory as to the scope and cause and operation of it all. Theistic Evolution allows the intervention of God at the creation of the primeval "fire-mist" and at the origin of life and the production of man's spiritual nature. The atheist denies any interference of a Creator at all. Haeckel says the best definition of Evolution is "the non-miraculous origin and progress of the universe." He and many others say that if the Creator is admitted at any point, He may as well be admitted all along. This is consistent Evolution.
The theistic and the atheistic evolutionist however agree in saying that man was descended from the brute, as to his body at least, and some even, as above shown, claim this descent for the whole man. This doctrine as to man is the vital part of the whole theory and in this all evolutionists are practically agreed. So that so far as their effect on Christian doctrine and Bible fact is concerned, all may be classed together.