Mankind has gone forward by the capture and control of the forces of Nature. This upward struggle began with the kindling of the first fire. The domestication of animal life marked another great step in the long ascent. The capture of the great physical forces, the discovery of coal and mineral oil, of gas, steam and electricity, and their adaptation to the everyday uses of mankind, wrought the greatest changes in the course of civilization. With the discovery of radium and radioactivity, with the recognition of the vast stores of physical energy concealed in the atom, humanity is now on the eve of a new conquest. But, on the other side, humanity has been compelled to combat continuously those great forces of Nature which have opposed it at every moment of this long indomitable march out of barbarism. Humanity has had to wage war against insects, germs, bacteria, which have spread disease and epidemics and devastation. Humanity has had to adapt itself to those natural forces it could not conquer but could only adroitly turn to its own ends. Nevertheless, all along the line, in colonization, in agriculture, in medicine and in industry, mankind has triumphed over Nature. But lest the recognition of this victory lead us to self-satisfaction and complacency, we should never forget that this mastery consists to a great extent in a recognition of the power of those blind forces, and our adroit control over them. It has been truly said that we attain no power over Nature until we learn natural laws and conform and adapt ourselves to them. The strength of the human race has been its ability not merely to subjugate the forces of Nature, but to adapt itself to those it could not conquer. And even this subjugation, science tells us, has not resulted from any attempt to suppress, prohibit, or eradicate these forces, but rather to transform blind and undirected energies to our own purposes. These great natural forces, science now asserts, are not all external. They are surely concealed within the complex organism of the human being no less than outside of it. These inner forces are no less imperative, no less driving and compelling than the external forces of Nature. As the old conception of the antagonism between body and soul is broken down, as psychology becomes an ally of physiology and biology, and biology joins hands with physics and chemistry, we are taught to see that there is a mysterious unity between these inner and outer forces. They express themselves in accordance with the same structural, physical and chemical laws. The development of civilization in the subjective world, in the sphere of behavior, conduct and morality, has been precisely the gradual accumulation and popularization of methods which teach people how to direct, transform and transmute the driving power of the great natural forces.