Educated folk keep to one another's company too much, leaving other people much like milk skimmed of its cream.

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.

Truth is better disengaged from error than torn from it.

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.

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

Error held as truth has much the effect of truth. In politics and religion this fact upsets many confident predictions.

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