Though she prefers that her name should not appear on the title-page, my wife has a share in this Volume also. For in writing it, and in writing the Principles, I have been aided and advised by her at every stage of the MSS. and the proofs; and thus the pages which are now submitted to the reader are indebted twice over to her suggestions, her judgment and her care.
Dr Keynes, Mr John Burnett and Mr J. S. Cree have read the proofs of the Chapter on Trade-Unions, and have given me helpful advice with regard to it from three different points. of view.
The changes in this edition follow those made in the third edition of my Principles. Book I. Ch. iv. and v. and Book III. Ch. vI. have been rewritten in order to make more clear how closely the economist adheres in substance to the methods of inference and judgment of ordinary life; and how thorough are the harmony and the mutual dependence between the analytical and the historical methods of economic study. In Book II., Ch. iv. and v. have been thrown together to make a new Chapter IV.; the old definition of Capital regarded from the point of view of the business man is retained; but Capital is defined from the general point of view as wealth which yields "income" in forms that are admitted in the broader use of the term in the market place. Book VI. Ch. 1. and II. have been recast, with further explanations, and a fuller rehearsal of the chief results obtained in the earlier Books.