Discussion of ‘‘Applied Eugenics” 81 
basis upon which students of both might 
build. 
The overworking of the ‘nature vs. 
nurture’’ antithesis has done incalculable 
harm in giving the discussion a partisan 
character. It should be supplanted, 
I think, by the conception that there are 
two parallel and interrelated processes, 
the biological and the social, equal in 
importance but quite different in charac- 
ter, supplementary to each other and 
not, properly speaking, in opposition 
to each other at all. The chief seat of 
the former is the germ-plasm; of the 
latter, the stream of psychical com- 
munication through which social organi- 
zation and development take place. 
Sociologists, _ economists, historians, 
jurists, political scientists, social workers 
and the like are primarily engaged with 
the latter, which (let biologists note) is 
a real system of organic life and not a 
mere “‘environment”’ of the germ-plasm. 
But as their whole process, biologically 
speaking, is founded on the germ-plasm, 
they must study eugenics. 
In a similar sense the biological pro- 
cess is based upon the social, which in 
general determines the environment in 
which the germ-plasm lives and, more 
particularly, the conditions of selec- 
tion which favor some types and sup- 
press others. Eugenists, then, should 
study sociology. 
I think it should be recognized, also, 
that human heredity is, in general, far 
more plastic than that of the lower 
animals. I mean, not that the princi- 
ples of heredity are different, but that 
the characters inherited are themselves, 
for the most part, plastic—teachable 
instincts instead of rigid, for example. 
A recognition of this would abate many 
controversies, reconciling, largely, the 
sociologist’s faith in education with the 
eugenist’s conviction of the impossibility 
of changing inherited traits. This princi- 
ple is, of course, good Darwinism, and 
you recognize it on page 406, where you 
say ‘‘All that man inherits is the capac- 
ity to develop along a certain line under 
the influence of proper stimuli . a 
I may add that a book I have recently 
published (‘‘Social Process,’’ Charles 
Scribner’s Sons) contains four chapters 
dealing with Social Factors in Biological 
Survival which deal somewhat more 
fully, though inadequately, with this 
line of thought. If you care to review 
these chapters, or the whole book, in the 
JOURNAL oF HEREDITY, I have no doubt 
the publishers will send you a copy for 
that purpose. 
Let me say again that I have read 
your book with profit and that 1 find 
myself agreeing with most of what you 
say relating to “the eugenic aspect of 
specific reforms.”’ 
Sincerely yours, 
CuHarLes H. Coo.ey. 
JOURNAL OF HEREDITY 
Washington, D. C., 
PROFESSOR CHARLES H. CooLey, 
Ann Arbor, Mich. 
Dear PROFESSOR COOLEY: 
Mr. Popenoe, has forwarded to me 
your letter to him on the subject of his 
book, “Applied Eugenics.” If agree- 
able to him and to yourself, I should 
like to publish this letter in the JouRNAL 
oF Herepiry, or perhaps the greater 
part of it, or perhaps you would make 
this the basis of a more extended re- 
view. I think it would be a fine idea 
to have the heredity environment prob- 
lem discussed from the sociological 
standpoint. 
For my part I have believed for a 
number of years that the tangle can 
only be unravelled by treating both 
factors as a problem of differences. 
This I had an inkling of, but no clear 
conception of at the time I published 
“Heredity in Royalty,’ 1906, for there 
I sometimes say that 90% is due to 
heredity. In another place I say that 
all the rough differences are due to 
differences in the germ-plasm, in spite 
of the considerable differences in the 
environment. This latter point of view 
is more elaborately worked out in an 
article published in the JoURNAL OF 
Herepity in 1917, called “Significant 
Evidence for Mental Heredity.” 
I do not see that your “‘stream of 
psychical communication through which 
social organization and development 
