The essays contained in the present volume were first published in the English periodicals—chiefly the Quarterly Reviews. They contain ideas of permanent interest, and display an amount of thought and labor evidently much greater than is usually bestowed on review articles. They were written with a view to ultimate republication in an enduring form, and were issued in London with several other papers, under the title of "Essays; Scientific, Political, and Speculative," first and second series;—the former appearing in 1857, and the latter in 1863.

The interest created in Mr. Spencer's writings by the publication in this country of his valuable work on "Education," and by criticisms of his other works, has created a demand for these discussions which can only be supplied by their republication. They are now, however, issued in a new form, and are more suited to develop the author's purpose in their preparation; for while each of these essays has its intrinsic and independent claims upon the reader's attention, they are all at the same time but parts of a connected and comprehensive argument. Nearly all of Mr. Spencer's essays have relations more or less direct to the general doctrine of Evolution—a doctrine which he has probably done more to unfold and illustrate than any other thinker. The papers comprised in the present volume are those which deal with the subject in its most obvious and prominent aspects.

Although the argument contained in the first essay on "Progress; its Law and Cause," has been published in an amplified form in the author's "First Principles," it has been thought best to prefix it to the present collection as a key to the full interpretation of the other essays.

To those who read this volume its commendation will be superfluous; we will only say that those who become interested in his course of thought will find it completely elaborated in his new System of Philosophy, now in course of publication.

The remaining articles of Mr. Spencer's first and second series will be shortly published, in a volume entitled "Essays; Moral, Political, and Æsthetic."