FIRST PRINCIPLES By HERBERT SPENCER. Published in 1855. PREFACE TO THE FOURTH EDITION: To the first edition of this work there should have been prefixed a definite indication of its origin and the misap prehensions that have arisen in the absence of such indica tions ought before now to have shown me the need for supplying it. Though reference was made in a note on the first page of the original preface to certain essays entitled Pro gress Its Law and Cause and Transcendental Pnysiology, as containing generalizations which were to be elaborated in the System of Philosophy there set forth in programme, yet the dates of these essays were not given nor was there any indication of their cardinal importance as containing, in a brief form, the general theory of evolu tion. No clear evidence to the contrary standing in the way, there has been very generally uttered and accepted the belief that this work, and the works following it, originated after, and resulted from, the special doctrine contained in Mr. Darwins Origin of Species The essay on Progress Its Law and Cause, co-exten sive in the theory it contains with chapters xv, xvi, xvii, and xx, in part ii, of this work, was first published in the Westminster Review for April, 1857 and the essay in which is briefly set forth the general truth elaborated in chapter xix, originally appeared under the title of The Ultimate Laws of Physiology, in the National Review for October, 1857. Further, I may point out that in the first edition of The Principles of Psychology published in July, 1855, mental phenomena are interpreted entirely from the evolution point of view and the words used in the titles of sundry chapters imply the presence, at that date, of ideas more widely applied in the essays just named. As the first edition of Origin of Species did not make its appearance till October, 1859, it is manifest that the theory set forth in this work and its successors had an origin independent of, and prior to, that which is com monly assumed to have initiated it. The distinctness of origin might, indeed, have been in ferred from the work itself, which deals with evolution at large inorganic, organic, and super-organic in terms of matter and motion and touches but briefly on those par ticular processes so luminously exhibited by Mr. Darwin. In 159 only p. 387 when illustrating the law of The Multiplication of Effects, as universally displayed, have I had occasion to refer to the doctrine set forth in Origin of Species pointing out that the general cause I had previously assigned for the production of divergent varieties of organisms would not suffice to account for all the facts without that special cause disclosed by Mr. Darwin. The absence of this passage would, of course, leave a serious gap in the general argument but the re mainder of the work would stand exactly as it now does. I do not make this explanation in the belief that the prevailing misapprehension will thereby soon be rectified for I am conscious that, once having become current, wrong beliefs of this kind long persist all disproofs not withstanding. Nevertheless, I yield to the suggestion that unless I state the facts as they stand I shall continue to countenance the misapprehension, and cannot expect it to cease. With the exception of unimportant changes in one of the notes, and some typographical corrections, the text of this edition is identical with that of the l st. May, 1880.