No man likes to have his intelligence or good faith questioned, especially if he has doubts about it himself.

Any belief worth having must survive doubt

The progress of evolution from President Washington to President Grant was alone evidence enough to upset Darwin

Absolute liberty is absence of restraint; responsibility is restraint; therefore, the ideally free individual is responsible to himself.

A teacher affects eternity; he can never tell where his influence stops.

Nothing in education is so astonishing as the amount of ignorance it accumulates in the form of inert facts.