Doubt is the beginning, not the end, of wisdom.

A man's own addition to what he learns is cement to bind an otherwise loose heap of stones into a structure of unity, strength, and use.

When a learner, in the fullness of his powers, comes to great truths unstaled by premature familiarity, he rejoices in the lateness of his lessons.

Nothing cools so fast as undue enthusiasm. Water that has boiled freezes sooner than any other.

Evolution pays and that is why there is evolution

Some young folks have wind-fall minds, prematurely detached from the tree of knowledge for a life-long sourness and pettiness.

A superstition is a premature explanation that overstays its time.