Excerpt from The Principles of Psychology, Vol. 1: The Data of Psychology This self-mobility which by its greater amount generally distinguishes higher animals from lower, and, indeed, enters largely into our conceptions of higher and lower, is displayed in several ways. We see it in the changes of attitude that are made without moving the body from place to place. We see it in the transference of the body as a whole through space: considering this transference apart from external resistances overcome. And we see it in the over coming Of resistances - both those of media and those due to gravity. All these, however, are manifestations of one ability - the ability to generate a force which either shows itself as momentum or would generate momentum but for a counterbalancing force. And it is in this general form that we are here concerned with this ability. We have to contemplate the inferior animals as being generators of very small quantities of actual or potential motion, and the higher animals as being generators of relatively-immense quantities of actual or potential motion. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.