Mr. Bagehot left behind him some materials for a book which promised to make a landmark in the history of economics, by separating the use of the older, or Ricardian, economic reasonings from their abuse, and freeing them from the discredit into which they had fallen through being often misapplied. Unfortunately he did not complete more than the examination of two of their postulates—the transferability of labour and capital. But these he treated with so much sagacity and suggestiveness as to give us great help in dealing with the others, and I have long been anxious that what he wrote about them should be published in a cheap form, so as to have a wide circulation among students…. [From the Preface, by Alfred Marshall]