It is a very old assertion, that a man who prudently sought his own interest would live a life of perfect virtue. This opinion is adopted by most of those Utilitarians who are least inclined to lay great stress upon religious motives; and as they maintain that every man necessarily pursues exclusively his own happiness, we return by another path to the old Platonic doctrine, that all vice is ignorance. Virtue is a judicious, and vice an injudicious, pursuit of pleasure. Virtue is a branch of prudence, vice is nothing more than imprudence or miscalculation.(17) He who seeks to improve the moral condition of mankind has two, and only two, ways of accomplishing his end. The first is, to make it more and more the interest of each to conform to that of the others; the second is, to dispel the ignorance which prevents men from seeing their true interest.(18) If chastity or truth, or any other of what we regard as virtues, could be shown to produce on the whole more pain than they destroy, or to deprive men of more pleasure than they afford, they would not be virtues, but vices.(19) If it could be shown that it is not for our own interest to practise any of what are admitted to be virtues, all obligation to practise them would immediately cease.(20) The whole scheme of ethics may be evolved from the four canons of Epicurus. The pleasure which produces no pain is to be embraced. The pain which produces no pleasure is to be avoided. The pleasure is to be avoided which prevents a greater pleasure, or produces a greater pain. The pain is to be endured which averts a greater pain, or secures a greater pleasure.(21)