Be sober, and to doubt prepense

The one condition under which all powers, and consequently the intellectual faculties, are developed, is exercise.

"Sordet cognita veritas" is a shrewd aphorism of Seneca. A truth, once known, falls into comparative insignificance.

The primary principle of education is the determination of the pupil to self-activity — the doing nothing for him which he is able to do for himself.

Truth like a torch, the more 'tis shook, it shines.

The question—Is Truth, or is the Mental Exercise in the pursuit of truth, the superior end?—this is perhaps the most curious theoretical, and certainly the most important practical, problem in the whole compass of philosophy.

[T]he sciences always studied with keenest interest are those in a state of progress and uncertainty: absolute certainty and absolute completion would be the paralysis of any study; and the last worst calamity that could befall man... …