Between mind and matter there exists the most intimate relationship. Immateriality, in its various phases of force, life, intellect, so far as human consciousness can grasp it, is inseparable from materiality. The body is but part of the soil on which it treads, and the mind can receive no impressions except through the organs of the body. The brain is the seat of thought and the organ of thought; neither can exist in a normal state apart from the other. As a rule, the power of the intellect is in proportion to the size and quality of the brain. Among animals, those of lowest order have the least brains; man, the most intellectual of animals, has relatively, if not absolutely, the largest brain. True, in some of the largest animals the cerebral mass is larger than in man, but, in its chemical composition, its convolutions, shape, and quality, that in man is superior; and it is in the quality, rather than in the quantity of the nervous tissues, that their superiority consists. Intelligence enters the brain by the organs of the senses, and through the nervous system its subtle influence radiates to every part of the body. All human activities are either mental or mechanical; nor will it be denied that mental activity is produced by mechanical means, or, that mechanical activity is the result of mental force. Corporeal motion is mental force distributed to the various parts of the body. The action of immaterial forces on the material substances of the human body manifestly accords with the action of immaterial forces elsewhere. All the physical and mechanical actions of the human body accord with the physical and mechanical forces elsewhere displayed. Man, we are told, was the last of all created things, but in the making of man no new matter was employed; nor in setting the body in motion can we discover that any new force was invented. Thus the heart beats upon mechanical principles; the eye sees, and the voice speaks in accordance with the general laws of optics and acoustics. To the observer, organic activity is but the product of combined inorganic forces. The same processes are at work, and in the same manner, in living and in so-called dead matter. Life, to all appearance, is but the result of combined chemical and mechanical processes. Assimilation, digestion, secretion, are explainable by chemistry, and by chemistry alone. The stomach is a chemical retort, the body a chemical laboratory. Carbon, oxygen, hydrogen, nitrogen, combine and separate in the body as out of the body. The blood circulates upon purely mechanical principles; all muscular action is mechanical. In the phenomena of life, the only perceptible difference is in the combinations of fundamental elements; yet chemistry and mechanics cannot produce a live body. With the foregoing well-recognized principles before us, let us now notice some few parallelisms between mechanical and social energetics.