In an inquiry into the productivity of labor some perplexity might be met with as to the share or the place of the brute forces of the human organism in the theory of production; but in relation to capital that question does not arise, except so far as these forces are involved in the production of the capital goods. As a parenthesis, more or less germane to the present inquiry into capital, it may be remarked that an analysis of the productive powers of labor would apparently take account of the brute energies of mankind (nervous and muscular energies) as material forces placed at the disposal of man by circumstances largely beyond human control, and in great part not theoretically dissimilar to the like nervous and muscular forces afforded by the domestic animals. FOOTNOTES: [1] Reprinted by permission from _The Quarterly Journal of Economics_, Vol. XXII, Aug., 1908. [2] "Assets" is, of course, not to be taken literally in this connection. The term properly covers a pecuniary concept, not an industrial (technological) one, and it connotes ownership as well as value; and it will be used in this literal sense when, in a later article, ownership and investment come into the discussion. In the present connection it is used figuratively, for want of a better term, to convey the connotation of value and serviceability without thereby implying ownership. [3] Barrows. [4] Motives of exploit and emulation, no doubt, play a serious part in bringing on the practice of ownership and in establishing the principles on which it rests; but this play of motives and the concomitant growth of institutions cannot be taken up here. _Cf._ _The Theory of the Leisure Class_, chaps. i, ii, iii. [5] _Cf._ H. Nieboer, _Slavery as an Industrial System_, chap. iv, sect. 12. [6] For a more extended discussion of this point see the _Quarterly Journal of Economics_, July, 1899, "The Preconceptions of Economic Science"; also _The Theory of Business Enterprise_, chap. iv, especially pp. 70-82. [7] Marx holds that the "primitive accumulation" from which capitalism takes its rise is a matter of force and fraud (_Capital_, Book I, chap. xxiv.). Sombart holds the source to have been landed wealth (_Moderne Kapitalismus_, Book II, Part II, especially chap. xii). Ehrenberg and other critics of Sombart incline to the view that the most important source was usury and the petty trade (_Zeitalter der Fugger_, chaps. i, ii). [8] The phrase "more or less" covers a certain margin of tolerance in respect of scale and method, which may be very appreciably wider in some lines of industry than in others, and which cannot be more adequately defined or described here within such space as could reasonably be allowed. The requirement of scale and method is enforced by competition. The force and reach of this competitive adjustment can also not be dealt with here, but the familiar current acceptance of the fact will dispense with details.