I. Tins Treatise will attempt to give an account of the fundamental nature of the universe, including man and society. It will not strive to cover all the boundaries of knowledge or to present all that is known of any one matter; rather, it will assume that history has furnished the main story, and it will endeavor only to clear up certain parts and to emphasize certain outlines in a way to bring the main features to more perfect view. The primary conceptions of physical and mental science will be given chief consideration. And this will be done with the main purpose of demonstrating that they may now be reduced to a single system of formulated knowledge most serviceable, in common, for all the sciences and for ethics, sociology, and religion. This task presents great difficulties, even in the style of writ ing it demands. It must take all sorts of readers into different regions of science, and make them familiar with details in ways difficult to most persons, though they seem unnecessarily element ary and tedious to each particular specialist. On the other hand, it must entice each specialist to go outside of his chosen domain and to interest himself in the summarizing of all departments of knowledge, consistently with one another, in ways he has, perhaps, grown to regard as futile for his particular work. Again, it must persuade the religious enthusiast that the path to be pursued is that in which his ardor may be most devoutly directed. From the outset, therefore, the author begs of all parties a serious patience worthy of the problem and of its fruits.