Ο David Hume, στο An Enquiry Concerning the Principles of Morals, σχολιάζει: "In general, we may observe, that the distinction of voluntary or involuntary was little regarded by the ancients in their moral reasonings; where they frequently treated the question as very doubtful, whether virtue could be taught or not? They justly considered, that cowardice, meanness, levity, anxiety, impatience, folly, and many other qualities of the mind, might appear ridiculous and deformed, contemptible and odious, though independent of the will. Nor could it be supposed, at all times, in every man's power to attain every kind of mental, more than of exterior beauty."