Those who place the emphasis upon heredity, in the attempt to discredit the value of thoughtful and painstaking control of the environment of the developing child, usually remind us that a man like Lincoln achieved power and distinction in spite of what we would ordinarily consider serious obstacles to complete development, whereas thousands of college graduates who have had all the advantages that trained tutors and guarded surroundings can give have developed into mediocre men and women--have even developed into vicious and criminal men and women. They will remind us that from a class of children that had the same teachers for many years has emerged a group of very distinct men and women; they will remind us that brothers and sisters with the identical "environment" turn out to be so different.
On the other hand, those who see nothing in "heredity" will point to the same Lincoln and ask confidently why his ancestors and his descendants do not show the same degree of power and achievement. They will point to the same family of brothers and sisters who had the same "heredity" and ask why they all turned out so differently. The black sheep proves just as much--and just as little--for one side of the argument as it does for the other.
There are, it is true, many people who say that they "do not believe" in either heredity or environment. Such people see the difficulties of the disputants and reject both alternatives. They prefer to say frankly that they do not understand the situation; that life is too complex to be solved by puny human intellects. Or they resort to some equally unintelligible explanation, such as "Fate" or "Nature"--which is but another way of saying that we never _can_ understand. On the other side stands the scientist who refuses to shut his eyes to _any_ established facts, and insists upon trying to understand as much as possible, though he may never hope to understand all.
But no one is prepared to say authoritatively that either heredity or environment is the exclusive or even the predominant factor in determining the character of the individual. Indeed, the voice of the scientist, which is the only authoritative voice we have in such matters, is telling us very plainly that the whole question of "heredity _or_ environment" is not a real question at all: we are confronted in every child with a case of heredity _and_ environment, and the practical question is how to control the latter so as to get the most from the former.