I. The Returns of Productive Agents. Carver's statement of the universal principle of diminishing returns, 558.—Other writers have believed that a stage of cessation of return would be reached, 559.—The possible formulae for expressing the law, 564.—II. The Productivity of Capital. (1) Definition and measure of capital. The word not explained by the writers using it in this connection, 565.—First definition: capital as intermediary products, 567.—Difficulties of measuring capital so denned, 568.— Second definition: capital as advances, 571.—Third definition: capital as value advanced during a certain period of time, 572.—In this last sense, capital can be measured, 575.—This definition has been used more or less implicitly by various economists, 579.—(2) Capital and the period of production; how related under the definition proposed, 582.—Böhm-Bawerk's failure to consider the duration of advances, 584. (3) The productivity of capital. Böhm-Bawerk's view: the roundabout process more productive. Criticisms of this view, 586.—Its author does not prove it, only illustrates it, 589.—The thesis false, 592.