180 ECONOMIC ESSAYS IN HONOR OF JOHN BATES CLARK 
i mT a ee . 
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 
ind. But somehow, we do bridge those gulfs. Human inter- 
: largely consists in so doing even if we cannot tell how we 
o it. The housewife knows the wants of her husband and chil- 
ren almost as well as she knows her own, and we may well take 
or granted that the other woman beside her, unless abnormal or 
nusual, has comparable wants both as an individual and as the 
presentative of her own family zroup. ANE 
hilosophic doubt is right and proper, but the problems of life 
annot, and do not, wait. One can even doubt the philosophic 
ropriety of our measurements of space, matter and time, and in 
act, Einstein has raised very definite doubts and possibly even 
overthrown what Newton seemed to have established. But prac- 
ically we go on measuring, and building in space and time, 
nd, for all practical purposes, our unproven ideas work. 
o economists cannot afford to be too academic and shirk the 
reat practical problems pressing upon them merely because these 
appen to touch on unsolved, perhaps insoluble, philosophical 
roblems. The psychologist has set the example by becoming a 
‘behaviorist.” He can thereby deal practically with phenomena 
he essential nature of which he confesses he cannot fathom. 
y common sense we cut our gordian knots. We may not know 
eally what goes on in the mind of a dog, but practically we can 
ell 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 
f another human being. Any normal housewife knows the heart’s 
esire of every member of her flock. SE 
Facing our problem, then, as a practical common sense problem, 
ather than as an academic and philesophical one, I venture to 
et up as a working hypothesis, that similar families have similar 
ants, that in particular, two average American working- 
en’s families which are of the same size and age and sex eon- 
titution, and which have the same food budgets will also have 
he same want-for-one-more unit of food; or again, that tro 
ypical American workingmen’s families which have the same 
ousing accommodation (assuming there has been opportunity to 
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