Entered, according to Act of Congress, in the year one thousand eight

hundred and sixty-two, by

HARPER & BROTHERS,

In the Clerk's Office of the District Court of the Southern District of New York.

Shortly will be published, by the same Author,

A HISTORY OF THE AMERICAN CIVIL WAR.

Three Volumes, 8vo.

Liers.

PREFACE.

AT the meeting of the British Association for the Advancement of Science, held at Oxford in 1860, I read an abstract of the physiological argument contained in this work respecting the mental progress of Europe, reserving the historical evidence for subsequent publication.

This volume contains that evidence. It is intended as the completion of my work on Human Physiology, in which man was treated of as an individual. In this he is considered in his social relation.

But the reader will also find, I think, that it is a history of the progress of ideas and opinions from a point of view heretofore almost entirely neglected. There are two methods of dealing with philosophical questions-the literary and the scientific. Many things which in a purely literary treatment of the subject remain in the background, spontaneously assume a more striking position when their scientific relations are considered. It is the latter method that I have used.

Social advancement is as completely under the control of natural law as is bodily growth. The life of an individual is a miniature of the life of a nation. These propositions it is the special object of this book to demonstrate.

No one, I believe, has hitherto undertaken the labor of arranging the evidence offered by the intellectual history of Europe in accordance with physiological principles, so as to illustrate the orderly progress of civilization, or collected the facts furnished by other branches of science with a view of enabling us to recognize clearly the conditions under which that progress takes place. This philosophical deficiency I have endeavored in the following pages to supply.

Seen thus through the medium of physiology, history presents a new aspect to us. We gain a more just and thorough appreciation of the thoughts and motives of men in successive ages of the world.

In the Preface to the second edition of my Physiology, published in 1858, it was mentioned that this work was at that time written. The 242241

changes that have been since made in it have been chiefly with a view of condensing it. The discussion of several scientific questions, such as that of the origin of species, which have recently attracted public attention so strongly, has, however, remained untouched, the principles offered being the same as presented in the former work in 1856.

NEW YORK, 1861.

POSTSCRIPT TO THE FIRST EDITION.

OWING to the Civil War, the publication of this work has been postponed for nearly two years. I do not regret the delay. The American reader, for whom it is chiefly intended, will find on many of its pages suggestions arising from the history of other people and other institutions, which may be profitably considered in connection with the great events now transpiring. When a nation has reached one of the epochs of its life, and is preparing itself for another period of progress under new conditions, it is well for every thoughtful man interested in its prosperity to turn his eyes from the contentions of the present to the accomplished facts of the past, and to seek for a solution of existing difficulties in the record of what other people in former times have done. NEW YORK, 1863.

PREFACE TO THE FOURTH EDITION.

THREE large editions of this work having been exhausted, I have carefully revised this—the fourth.

For the mark of approval and encouragement thus given me, I return my sincere thanks. Though I felt assured that the time had come when a book treating of history in the scientific method might be offered to the consideration of the public, I was not prepared to expect that my work would find so many readers both in America and Europe, and that so many editions, reprints, and translations of it would be called for.

To those of my literary friends who have reviewed it, both favorably and otherwise, I am greatly indebted: to the former for the generosity of their criticisms, to the latter for the valuable suggestions they have made. It was not to be supposed that a work of such wide scope, dealing with so many contested questions of profound interest, could be written in a manner to come up to the ideal of every reader. The great success that has rewarded this attempt has altogether exceeded my most sanguine anticipations.

From that success I hope that those who have been led to consider historical questions in the manner here presented will take encouragement. There can now be no doubt that the public approval is given to that method.

It will be seen, from a comparison of this edition with the preceding ones, that the Publishers have made considerable improvements, so far as its typographical appearance is concerned. With these additional recommendations, I ask for it continued favor.

NEW YORK, 1865.