Sec. 3] PSYCHIC INCOME 167 
body, and, although credited to the medicine, should be 
debited to the body, just as the services of a carpenter are 
credited to him but debited to the house which he mends. 
So the services of a dentist, far from producing any immedi- 
ate satisfactions, have for the moment quite an opposite 
effect, but result later in better service of one’s own teeth. 
They are credited to the dentist, but debited to the body. 
The “consumption,” or use of food, though it is a service of 
the food, is a disservice of the body; for food stands in the 
same relation to the body as fuel to a furnace or repairs to 
a house. The final income consists of the subjective sat- 
isfaction of appetite and the other satisfactions which 
the intake of food enables the body to yield to the mind. 
These include not simply the immediate gratification of the 
palate, but the promotion of pleasant sensations or the 
avoidance of unpleasant ones later on. In other words, 
the consumption of food, by preserving health and main- 
taining life, enables the body to yield better and longer- 
continued income to the mind in future years, just as the 
repairs on a house enable it to yield shelter a long time after 
the repairs are made. 
§3 
These and other illustrations will show that, if we in- 
clude the body as a transforming instrument, while we 
must credit with their respective services all these outside 
agencies, such as food, clothing, dwelling, furniture, orna- 
ments, and other articles which, as it were, bombard a 
man’s sensory system, we must also at the same time debit 
the body with these same items. In this case the only sur- 
viving credit items after these equal debits and credits are 
canceled are the resulting final satisfactions in the human 
mind. In other words, in order that the external world 
should become effective to man, the human body must be 
considered as the last transforming instrument. Just as 
there is a gradual transformation of services through the