I venture to define science as a series of interconnected concepts and conceptual schemes arising from experiment and observation and fruitful of further experiments and observations. The test of a scientific theory is, I suggest, its fruitfulness.

Science advances, not by the accumulation of new facts, but by the continuous development of new concepts.

Some of mankind's most terrible misdeeds have been committed under the spell of certain magic words or phrases.

A conceptual scheme is never discarded merely because of a few stubborn facts with which it cannot be reconciled; a conceptual scheme is either modified or replaced by a better one, never abandoned with nothing left to take its place.

The dignity of man is vindicated as much by the thinker and poet as by the statesman and soldier.

The stumbling way in which even the ablest of the scientists in every generation have had to fight through thickets of erroneous observations, misleading generalizations, inadequate formulation, and unconscious prejudice is rarely appreciated by those who obtain their scientific knowledge from textbooks.

Public education is a great instrument of social change. Through it, if we so desire, we can make our country more nearly a democracy without classes. To do so will require the efforts of us all-teachers, administrators, taxpayers and statesmen. Education is a social process, perhaps the most important process in determining the future of our country; it should command a far larger portion of our national income than it does today.