CLARK'S REFORMULATION OF THE CAPITAL CONCEPT 141 
artificial, produced, goods and to include as capital anything 
(or at least its value) that is the durable foundation of a use 
that has value. 
Very similar ideas were developed by Carl Rodbertus in the 
thirties and forties, most significant because of the great influence 
they exercised upon later thinkers in the period of developing 
German state socialism after 1870. Especially Adolf Wagner 
acknowledged his profound indebtedness to Rodbertus.® To 
Wagner is due the much wider circulation and influence in the 
last quarter of a century of these ideas which he restated and 
endorsed.” Wagner credits Rodbertus with “the essential dis- 
tinction between capital in the purely economic sense as any stock 
of material agents and means of production, and capital in the 
historico-legal sense as capital-possessions.” He cites the state- 
ment of Knies that political economy uses capital in two senses, 
as concrete means of production, and as a stock of goods acquired 
by an owner. Both Wagner and Knies recognize the double 
meaning of capital as a tool in economic processes (technological 
sense) and as a source of private income (acquisitive sense), the 
distinction on which so much of the thought of Thorstein Veblen 
as well as of Karl Marx, seems to have been based. When Knies 
says approvingly that what has been called capital is “funda- 
mentally nothing but a mere abstraction,” * the expression might 
be the original of Clark’s “entity,” “this abstract conception of 
capital.” * 
Clark, in common with all other Americans pursuing graduate 
economic studies in Germany, must have become familiar with 
these ideas. Yet why did no trace of them ever appear in the 
writings of other students returning from Germany, or even in 
Clark’s writings, until 1888? Is not the explanation to be found 
in the fact that Americans went abroad with minds already cast 
in the mold of the Ricardian-Mill “orthodox” scheme of dis- 
tributive theory, and these concepts persisted. It was possible 
for these students to acquire a zeal for displacing (or for supple- 
' The ideas of Rodbertus on capital are scattered throughout his writ- 
ings, but perhaps more systematically presented in his work Das Kapital, 
written 1850-51 but published first in 1885 by A. Wagner and T. Kozak. 
(Known to the writer only in the French translation, Paris, 1904.) 
* See Wagner's Grundlegung, 3rd. ed., 1892, p. 307 ff. 
* Knies, op. cit., p. 43. 
‘ Clark, op. cit., p. 11.