Every man carries about him a touchstone, if he will make use of it, to distinguish substantial gold from superficial glitterings, truth from appearances. And indeed the use and benefit of this touchstone, which is natural reason, is spoiled and lost only by assuming prejudices, overweening presumption, and narrowing our minds.
John LockeNobody is made anything by hearing of rules, or laying them up in his memory; practice must settle the habit of doing, without reflecting on the rule; and you may as well hope to make a good painter, or musician, extempore, by a lecture and instruction in the arts of music and painting, as a coherent thinker, or a strict reasoner, by a set of rules, showing him wherein right reasoning consists.
John LockeMan is not permitted without censure to follow his own thoughts in the search of truth, when they lead him ever so little out of the common road.
John Locke