we shall continue
to use it, with the implications that have just been outlined.

The antithesis of nature and nurture is not a new one; it was met long
ago by biologists and settled by them to their own satisfaction. The
whole body of experimental and observational evidence in biology tends
to show that the characters which the individual inherits from his
ancestors remain remarkably constant in all ordinary conditions to which
they may be subjected. Their constancy is roughly proportionate to the
place of the animal in the scale of evolution; lower forms are more
easily changed by outside influence, but as one ascends to the higher
forms, which are more differentiated, it is found more and more
difficult to effect any change in them. Their characters are more
definitely fixed at birth.[1]

It is with the highest of all forms, Man, that we have now to deal. The
student in biology is not likely to doubt that the differences in men
are due much more to inherited nature than to any influences brought to
bear after birth, even though these latter influences include such
powerful ones as nutrition and education within ordinary limits.

But the biological evidence does not lend itself readily to summary
treatment, and we shall therefore examine the question by statistical
methods.[2] These have the further advantage of being more easily
understood; for facts which can be measured and expressed in numbers are
facts whose import the reader can usually decide for himself: he is
perfectly able to determine, without any special training, whether twice
two does or does not make four. One further preliminary remark: the
problem of nature vs. nurture can not be solved in general terms; a
moment's thought will show that it can be understood only by examining
one trait at a time. The problem is to decide whether the differences
between the people met in everyday life are due more to inheritance or
to outside influences, and these differences must naturally be examined
separately; they can not be lumped together.

To ask whether nature in general contributes more to a man than nurture
is futile; but it is not at all futile to ask whether the differences in
a given human trait are more affected by differences in nature than by
differences in nurture. It is easy to see that a verdict may be
sometimes given to one side, sometimes to the other. Albinism in
animals, for instance, is a trait which is known to be inherited, and
which is v