180 ECONOMIC ESSAYS IN HONOR OF JOHN BATES CLARK 
this answer is that, in actual practical human life, we do pro- 
ceed on just such assumptions. Academically we may have 
philosophic doubts as to bridging the gulf between mind and 
mind, or even between one time and another time for the same 
mind. But somehow, we do bridge those gulfs. Human inter- 
course largely consists in so doing even if we cannot tell how we 
do it. The housewife knows the wants of her husband and chil- 
dren almost as well as she knows her own, and we may well take 
for granted that the other woman beside her, unless abnormal or 
unusual, has comparable wants both as an individual and as the 
representative of her own family group. 
Philosophic doubt is right and proper, but the problems of life 
cannot, and do not, wait. One can even doubt the philosophic 
propriety of our measurements of space, matter and time, and in 
fact, Einstein has raised very definite doubts and possibly even 
overthrown what Newton seemed to have established. But prac- 
tically we go on measuring, and building in space and time, 
and, for all practical purposes, our unproven ideas work. 
So economists cannot afford to be too academic and shirk the 
great practical problems pressing upon them merely because these 
happen to touch on unsolved, perhaps insoluble, philosophical 
problems. The psychologist has set the example by becoming a 
“behaviorist.” He can thereby deal practically with phenomena 
the essential nature of which he confesses he cannot fathom. 
By common sense we cut our gordian knots. We may not know 
really what goes on in the mind of a dog, but practically we can 
tell by his behavior when he is hungry, or pleased. We have some- 
how learned to interpret the wagging of his tail, and the sound 
of his bark. Even more have we learned to interpret the feelings 
of another human being. Any normal housewife knows the heart’s 
desire of every member of her flock. 
Facing our problem, then, as a practical common sense problem, 
rather than as an academic and philosophical one, I venture to 
set up as a working hypothesis, that similar families have similar 
wants, that in particular, two average American working- 
men’s families which are of the same size and age and sex con- 
stitution, and which have the same food budgets will also have 
the same want-for-one-more unit of food; or again, that two 
typical American workingmen’s families which have the same 
housing accommodation (assuming there has been opportunity to