Kuhn tain data uncritically, and declines to challenge the elements between which its own laws' obtain, and from which its own deductions are carried on. Psychology, the science of finite individual minds, assumes as its data (1) thoughts and feelings, and (2) a physical world in time and space with which they coexist and which (3) they know. Of course these data themselves are discussable; but the discussion of them (as of other elements) is called metaphysics and falls outside the province of this book. This book, assuming that thoughts and feelings exist and are vehicles of knowledge, thereupon contends that psychology when she has ascertained the empirical correlation of the various sorts of thought or feeling with definite conditions of the brain, can go no farther-can go no farther, that is, as a natural science. If she goes farther she becomes metaphysical. All attempts to explain our phenomenally given thoughts as products of deeper-lying entities (whether the latter be named 'Soul,' 'Transcendental Ego,' 'Ideas,' or 'Elementary Units of Consciousness') are metaphysical. This book consequently rejects both the associationist and the spiritualist theories; and in this strictly positivistic point of view consists the only feature of it for which I feel tempted to claim originality. Of course this point of view is anything but ultimate. Men must keep thinking; and the data assumed by psychology, just like those assumed by physics and the other natural sciences, must some time be overhauled. The effort to overhaul them clearly and thoroughly is metaphysics; but metaphysics can only perform her task well when distinctly conscious of its great extent. Metaphysics fragmentary, irresponsible, and half-awake, and unconscious that she is metaphysical, spoils two good things when she injects herself into a natural science. And it seems to me that the theories both of a spiritual agent and of associated 'ideas' are, as they figure in the psychology-books, just such metaphysics as this. Even if their results be true, it would be as well to keep them, as thus presented, out of psychology as it is to keep the results of idealism out of physics. I have therefore treated our passing thoughts as inte gers, and regarded the mere laws of their coexistence with brain-states as the ultimate laws for our science. The reader will in vain seek for any closed system in the book. It is mainly a mass of descriptive details, running out into queries which only a metaphysics alive to the weight of her task can hope successfully to deal with. That will perhaps be centuries hence; and meanwhile the best mark of health that a science can show is this unfinished-seeming front. The completion of the book has been so slow that several chapters have been published successively in Mind, the Journal of Speculative Philosophy, the Popular Science Monthly, and Scribner's Magazine. Acknowledgment is made in the proper places. The bibliography, I regret to say, is quite unsystematic. I have habitually given my authority for special experimental facts; but beyond that I have aimed mainly to cite books that would probably be actually used by the ordinary American college-student in his collateral reading. The bibliography in W. Volkmann von Volkmar's Lehrbuch der Psychologie (1875) is so complete, up to its date, that there is no need of an inferior duplicate. And for more recent references, Sully's Outlines, Dewey's Psychology, and Baldwin's Handbook of Psychology may be advantageously used. Finally, where one owes to so many, it seems absurd to single out particular creditors; yet I cannot resist the temptation at the end of my first literary venture to record my gratitude for the inspiration I have got from the writings of J. S. Mill, Lotze, Renouvier, Hodgson, and Wundt, and from the intellectual companionship (to name only five names) of Chauncey Wright and Charles Peirce in old times, and more recently of Stanley Hall, James Putnam, and Josiah Royce. HARVARD UNIVERSITY, August 1890. CONTENTS. CHAPTER I. THE SCOPE OF PSYCHOLOGY, Mental Manifestations depend on Cerebral Conditions, 1. Reflex, semi-reflex, and voluntary acts, 12. The Frog's nerve- CHAPTER III. ON SOME GENERAL CONDITIONS OF BRAIN-ACTIVITY, The summation of Stimuli, 82. Reaction-time, 85. Cerebral Due to plasticity of neural matter, 105. Produces ease of PAGE . 1 12 81 CHAPTER V. THE AUTOMATON-THEORY, The theory described, 128. Reasons for it, 188. Reasons Evolutionary Psychology demands a Mind-dust, 146. Some PAGE 145 CHAPTER VII. THE METHODS and Snares OF PSYCHOLOGY, Psychology is a natural Science, 183. Introspection, 185. CHAPTER VIII. . 183 Time relations: lapses of Consciousness-Locke v. Descartes, Consciousness tends to the personal form, 225. It is in con- . 199 224 CHAPTER X. THE CONSCIOUSNESS OF SELF, The Empirical Self or Me, 291. Its constituents, 292. The 291 |