116 NATURE OF CAPITAL AND INCOME [Cmae. VII 
instruments is the entire group of instruments constituting 
the entire capital of a community, the net total of their 
services and disservices is the entire income of the com- 
munity. This is social income. If the group be the entire 
property of an individual —the rights which he owns, 
complete or partial, in instruments — the net total of the 
services and disservices to which he is thus entitled consti- 
tutes his income. This is individual income. 
In science, the chief test of a definition is its adaptability 
to analysis. Judged by this test, none of the current con- 
cepts of income which we have passed in review can 
claim to be adequate; for we have found them subject to 
the confusions of capital and income, and of double count- 
ing. A secondary test is that a working definition should 
also fit into, or rather, give clear and consistent outlines 
to the vague notions of income which we find ready made in 
the actual world of business and accounts. 
Of our own concept of income, as consisting exclusively 
of services, we shall endeavor to show that it includes the 
commercial bookkeeper’s concept of “money income” ; 
that it is coextensive with the popular notions of income, 
including what those notions include and excluding what 
they exclude; that it affords a place for the usage by which 
sinking funds are reckoned and justifies the phrase “living 
beyond income”; that it avoids double counting auto- 
matically and without the necessity for the exercise of judg- 
ment in each special case; that it makes capital and income 
strictly correlative but never in danger of being confused; 
and last, but not least, that it lends itself readily io economic 
analysis and serves as a foundation for the theory of interest. 
The concept of income to be elaborated is similar to 
several which have been put forward by other writers. 
Tt is almost identical with that of Edwin Cannan! it 
' See History of the Theory of Production and Distribution ; Elemen- 
tary Political Economy; and “What is Capital?” Economic Journal, 
1897.