"A word or two seems necessary by way of explanation of the publication of a biography of Mr. Herbert Spencer, within a few years of the publication of his voluminous Autobiography. Twenty-eight years ago, while I was at home on furlough, Mr. Spencer obtained from me a promise to write his Life. In subsequent years, partly owing to his fears that his own life might not be prolonged, and partly because he thought that my absence in India would render it difficult, if not impossible, for me to fulfil my promise, he made other arrangements. These other arrangements, however, fell through. Hence the question, in a letter to me, dated 10 May, 1893: "Does the assent which you gave years ago still hold, and is it likely to hold?" On receiving an affirmative answer, Mr. Spencer had the following paragraph inserted in his Will:--"I request that the said David Duncan will write a Biography in one volume of moderate size, in which shall be incorporated such biographical materials as I have thought it best not to use myself, together with such selected correspondence and such unpublished papers as may seem of value, and shall include the frontispiece portrait and the profile portraits, and shall add to it a brief account of the part of my life which has passed since the date at which the Autobiography concludes." The existence of the Autobiography, which covers sixty-two years of Mr. Spencer's life, has added to the difficulties of my task. The road traversed by him has had to be traversed by me; but I have endeavoured to avoid needless repetition, while omitting nothing that has seemed necessary to form a continuous and complete narrative. Of the remaining twenty-one years, the volume now published constitutes the only authoritative record. To avoid multiplication of references, a note has been inserted at the beginning of each chapter--from chapter i. to chapter xvi.--to show the corresponding chapters in the Autobiography. I have not aimed at giving an exposition or criticism of the philosophy of Evolution. Even had such an aim been in accordance with Mr. Spencer's wishes, it would have been impossible, within the prescribed limits, to do justice either to the Life or to the Philosophy, had the attainment of both ends been attempted"--Preface. (PsycINFO Database Record (c) 2010 APA, all rights reserved).