170 NATURE OF CAPITAL AND INCOME [Crar. X

prenticeship is, as it were, an investment in the body, to be
returned at a later time (with interest), just as the planting
 of a tree is an investment in the tree in order that its
fruit may be secured in later years. At the time of tree
planting there is no net income, for the work credited the
tree planter is debited the tree; it is only when in after
years the tree bears fruit or other product that any return
is obtained from the planting. Similarly, the work of
teaching the apprentice should be credited to the teacher
and debited to the apprentice’s body; the final satisfactions
will not come until the acquired knowledge becomes
effective. All this can be faithfully recorded only in the
complete accounting which includes subjective income.
The same principles apply to any training or education
for a profession. When a young man studies law, medicine,
 journalism, music, or prepares for any other profession,
 he is investing in his own person, with the hope that
the sums thus invested may ultimately be returned to him
(with interest). The same is true of physical training.
Many of the most successful men are those who, like
President Roosevelt, in early life saw the wisdom of
developing a strong body, and in consequence have increased
 their productive power in mature years.

§5

The second point at which subjective and objective
income diverges is found in occupations whose special gratification
 or irksomeness renders their return in psychical income
 widely different from their return in objective income.
This is frequent in conditions of labor. Properly speaking,
objective income takes no account of the toil of the laborer.
The workingman who earns $2 a day earns double the objective
 income of one who earns $1 a day. Yet if the work
of the former is difficult, loathsome, or dangerous, it may
well be that many would prefer the nominally smaller income
 rather than endure these disadvantages. These facts