This book treats of the religion of Abraham Lincoln; but it does not consider his religion as wholly expressed in his theological opinions. Important as it is that a man should think correctly on all subjects, and especially on a subject of such transcendent value, religion is more than a matter of opinion. We cannot adequately consider religion apart from life. Abraham Lincoln's life was an evolution, and so was his religion. In a way which this volume will seek to set forth, Lincoln was himself a believer in evolution, and his life and religion were in accord with this process as he held it. This book is, therefore, more than an essay on the religion of Lincoln, unless religion be understood as inclusive of all that is normal in life. It deals, therefore, with the life, as well as with the opinions, of Lincoln; and it considers both life and opinion as in process of development in each of the successive stages of his career. In this respect the present book may claim some distinctive place in the literature of this subject. Other books have drawn sharp contrasts between the supposed religious opinions of Lincoln's youth and those which he is believed to have cherished later. This book undertakes what may be termed a study of the evolution of the spiritual life of Abraham Lincoln. The author is not aware that this has been done before in quite this way. The author acknowledges his obligations to many friends for their assistance in the preparation of this volume. Mr. Jesse W. Weik, of Greencastle, Indiana, associate of Mr. Herndon in the preparation of his Life of Lincoln, and owner of the Herndon manuscripts, has been generous to me. Mrs. Clark E. Carr, of Galesburg, Illinois, widow of my honored friend, and the friend of Lincoln, Colonel Carr, author of "Lincoln at Gettysburg," has placed at my disposal all her husband's books and papers. Mr. Judd Stewart, of New York City, owner of one of the largest collections of Lincolniana, has assisted me. President John W. Cook of the Northern Illinois State Normal School has suggested important lines of research. Mr. John E. Burton, of Lake Geneva, Wisconsin, whose collection of Lincoln books was once the largest in America, has sold me some of his chief treasures, and imparted to me much of the fruit of his experience. Mr. O. H. Oldroyd, of Washington, owner of the famous Lincoln Collection, and custodian of the house where Lincoln died, has, on two visits, placed all that he has within my reach. To these, and to a considerable number of men and women who knew Lincoln while he was yet living, and to many others whom I cannot name, my thanks are due. I regret that one great collection, consisting, however, more largely of relics than of manuscripts, is so largely packed away that it has not been of much use to me. Mr. Charles F. Gunther of Chicago has, however, produced for me such Lincoln material as seemed to him to bear upon my quest, and I acknowledge his courtesy.