For to be possessed of a vigorous mind is not enough; the prime requisite is rightly to apply it. The greatest minds, as they are capable of the highest excellences, are open likewise to the greatest aberrations; and those who travel very slowly may yet make far greater progress, provided they keep always to the straight road, than those who, while they run, forsake it.
~René Descartes, Discourse on the Method
A monthly thread for posting rationality-related quotes you've seen recently (or had stored in your quotesfile for ages).