Edward L. Thorndike, answered from the texts and cited to the page.
The original nature of man is given, not made. Each child comes into the world with a stock of instincts, capacities, and limits that are the gift of his ancestry, and education works only within the range that this original nature allows.1 I hold, on the evidence of the tests and of the study of families and twins, that individual differences in intelligence and in the special abilities are very largely inborn — that of two children given the same schooling, the difference in what they make of it is chiefly a difference in the nature they brought to it.2
What is true of individuals is true, in the average, of groups. To deny this — to suppose that all are born equal and that circumstance alone divides them — is to fly in the face of the measurements and to build education and society on a sentimental falsehood. The abler are a nation's chief resource; to identify, cultivate, and multiply them is sound policy, and to pretend that nurture can make a dull child brilliant is to waste effort and to misunderstand the facts of inheritance.34
My measurements are not as yet adequate for a full conclusion; but it is extremely unlikely that they will show correlations between identical twins of more than.70. The importance to educational theory of a recognition of the fact of original nature and of exact knowledge of its relative share in determining life's progress is obvious.Educational Psychology, pp. 58–59
The environment may always work to increase or diminish original differences, though how far it may do so is a question. But that environment can alter original natures and mask their intrinsic qualities gives no reason to deny the existence of these qualities. Their existence, their extent and their degree of specialization can be discovered only by a comparison of individuals subjected to the same environment.Educational Psychology, p. 55
The important thing for the common good, for all men, is that the top should be high — that much should be achieved. To the absolute welfare of all men together education is the great contributor.Educational Psychology Vol 3 Mental Work and Fatigue, pp. 312–313
The important thing for the common good, for all men, is that the top should be high — that much should be achieved. To the absolute welfare of all men together edu- cation is the great contributor.Educational Psychology Briefer Course
Thorndike's strong hereditarianism sits at the center of the century's most contested debate and is among his most criticized positions. The environmentalist reformers of his own day, and the later demonstration of large environmental effects on measured ability (schooling, nutrition, the Flynn effect, the malleability of early development), told heavily against the claim that ability is overwhelmingly inborn and against his extension of hereditarianism to group and racial averages, which is now scientifically repudiated on the same grounds that undercut Galton. Modern behavior genetics grants substantial heritability of measured intelligence within groups while also finding large environmental effects and denying that between-group differences can be read as genetic — a verdict that vindicates part of Thorndike's individual-differences claim and rejects the hereditarian social and racial conclusions he drew from it.