Finally, one other suggestion must be made. Spencer, after a long and involved argument, concludes (or proves as he believes) that the great law of evolution is a necessity that follows from the law of the persistence of force. In chapter two of this series, the scientific conception of the persistence of force was identified with the operations of the Holy Spirit, as taught by Joseph Smith. This Spirit is behind all phenomena; by it as a medium, God works his will with the things of the universe, and enables man to move on to eternal salvation, to advance, and become a God; every law is of necessity a result of the operation of this Spirit. Here, again, the "Mormon" prophet anticipated the world of science; and his conceptions are simplier and more direct than those invented by the truth-seekers, who depended upon themselves and their own powers. Marvelous is this view of the founder of "Mormonism." Where did he learn in his short life, amidst sufferings and persecution such as few men have known, the greatest mysteries of the universe! Chapter XV. THE PLAN OF SALVATION. [Sidenote: Why am I on earth?] In the preceding chapter the law of evolution was shown to be the cementing law of nature, which explains the destiny of man. To live is to change, and (if the change is right) to grow. Through all the ages to come righteous man will increase in complexity and will grow towards a condition of greater knowledge, greater power and greater opportunity. While the great law of evolution may be quite sufficient for the general survey, it does not explain the special conditions amidst which organized intelligences find themselves. Man asks, Why am I on earth? Science is silent. Up to the present time, many scientific men have not found it necessary to postulate an intelligent force behind the phenomena of nature, which would explain our earthly existence. The Mormon answer to this question lies in the Mormon doctrine of the plan of salvation. There can be no attempt to harmonize the Mormon plan with that of science, for science has none; but, that the Mormon plan of salvation is strictly scientific, and rests upon the irrevocable laws of the universe can certainly be demonstrated. [Sidenote: Perfection comes only when matter, spirit and intelligence are associated.] Fundamental, in the doctrines of Joseph, is the statement that all intelligence is eternal; and that God at the best is the organizer of the spirits of men. The ether of science has been compared with the Holy Spirit of Mormonism. The spirit body may be likened to an ether body of man, and is the condition of his original existence. From the original condition, at man's spiritual birth, under the law of evolution he has steadily grown in complexity, which means in power.