34 THE MISMEASURE OF MAN
ing of the world's complexity, nature vs. nurture must rank among
the top two or three (a phony division only enhanced by the eu-
phony of these names). I don't think that any smoke screen infuri-
ates me more than the biodeterminist's frequent claim "But we are
the sophisticated ones; our opponents are pure environmentalists,
supporters of nurture alone; we recognize that behaviors arise by
an interaction of nature and nurture." May I then emphasize again,
as the text of The Mismeasure of Man does throughout, that all parties
to the debate, indeed all people of good will and decent information,
support the utterly uncontroversial statement that human form and
behavior arise from complex mixtures of genetic and environmen-
tal influences.
Errors of reductionism and biodeterminism take over in such
silly statements as "Intelligence is 60 percent genetic and 40 percent
environmental." A 60 percent (or whatever) "heritability" for intelli-
gence means no such thing. We shall not get this issue straight until
we realize that the "interactionism" we all accept does not permit
such statements as "Trait x is 29 percent environmental and 71
percent genetic." When causative factors (more than two, by the
way) interact so complexly, and throughout growth, to produce an
intricate adult being, we cannot, in principle, parse that being's be-
havior into quantitative percentages of remote root causes. The
adult being is an emergent entity who must be understood at his
own level and in his own totality. The truly salient issues are mallea-
bility and flexibility, not fallacious parsing by percentages. A trait
may be 90 percent heritable, yet entirely malleable. A twenty-dollar
pair of eyeglasses from the local pharmacy may fully correct a defect
of vision that is 100 percent heritable. A "60 percent" biodeterminist
is not a subtle interactionist, but a determinist on the "little bit preg-
nant" model.
Thus, for example, Mr. Murray, in high dudgeon about my
review of The Bell Curve (reprinted here as the first essay in the
concluding section), writes in the Wall Street Journal (December 2,
1994), excoriating my supposed unfairness to him:
Gould goes on to say that "Herrnstein and Murray violate fairness by con-
verting a complex case that can yield only agnosticism into a biased brief for
permanent and heritable differences." Now compare Mr. Gould's words
with what Richard Herrnstein and I wrote in the crucial paragraph summa-
rizing our views on genes and race: "If the reader is now convinced that