alien environment.

Our present knowledge of the nature and history of human mentality enables
us to learn many lessons that have a direct practical value, although it
is impossible under the present limitations to give them the full
discussion they deserve. Starting from the dictum that physical
inheritance provides the mechanism of intellect, education and training of
any kind prove to be effective as agents for developing hereditary
qualities or for suppressing undesirable tendencies. Just as wind-strewn
grains of wheat may fall upon rock and stony soil and loam, to grow well
or poorly or not at all according to their environmental situations, so
children with similar intellectual possibilities would have their growth
fostered or hampered or prevented by the educational systems to which they
were subjected. But the common-sense of science demonstrates that the
mental qualities themselves could not be altered _in nature_ by the
circumstances controlling their development any more than the hereditary
capability of the wheat grains to produce wheat would be altered by the
character of the ground upon which they fell. Education and training thus
find their sphere of usefulness is developing what it is worth while to
bring out, and inhibiting the growth of what is harmful. That heredity in
mental as well as in physical aspects provides the varying materials with
which education must deal is a fundamental biological fact which is too
often disregarded. It would be as futile for an instructor to attempt the
task of forcing the children in a single schoolroom into the same mental
mold, as it would be for a gymnasium master to expect that by a similar
course of exercise he could make all of his students conform to the same
identical stature, the same shape of the skull, or the same color of the
eye and hair.

* * * * *

Before leaving the subject of mental evolution we must return to the
conception of inseparable mind and matter with which the present
discussion began. The whole problem of human mental evolution is solved
when we accept the conclusion that the nervous mechanism and the total
series of its functional operations have evolved together in the
production of the human brain and human faculty. The case regarding the
physical organs rests solidly on the basis of the evidences outlined in a
previous chapter; the special examination of purely mental phenomena has
likewise been made in t