A tree nowhere offers a straight line or a regular curve, but who doubts that root, trunk, boughs, and leaves embody geometry?

Form may be of more account than substance. A lens of ice will focus a solar beam to a blaze.

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

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

Let truth be a banner big enough to hide the man who holds it up.

We despair of changing the habits of men, still we would alter institutions, the habits of millions of men.

A superstition is a premature explanation that overstays its time.