entific
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 labour 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 endeavoured 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
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._

PREFACE TO THE REVISED EDITION.

Many reprints of this work having been issued, and translations
published in various foreign languages, French, German, Russian, Polish,
Servian, &c., I have been induced to revise it carefully, and to make
additions wherever they seemed to be desirable. I therefore hope that it
will commend itself to the continued approval of the public.

_November, 1875._

CONTENTS.

CHAPTER I.

ON THE GOVERNMENT OF NATURE BY LAW.

_The subject of this Work proposed.--Its difficulty._

_Gradual Acquisition of the Idea of Natural Government by
Law.--Eventually sustained by Astronomical, Meteorological,
and Physiological Discoveries.--Illustrations from Kepler's
Laws, the Trade-winds, Migrations of Birds, Balancing of
Vegetable and Animal Life, Variation of Species and their
Permanence._

_Individual Man is an Emblem of Communities, Nations, and
Universal Humanity.--T