Section 12: The Mind Must Be Stable explained simply

XII. “They are ill at ease,” replies he, “because many things arise which distract their thoughts, and their minds are disquieted by conflicting opinions.” I admit that this is true: still these very men, foolish, inconsistent, and certain to feel remorse as they are, do nevertheless receive great pleasure, and we must allow that in so doing they are as far from feeling any trouble as they are from forming a right judgment, and that, as is the case with many people, they are possessed by a merry madness, and laugh while they rave. The pleasures of wise men, on the other hand, are mild, decorous, verging on dulness, kept under restraint and scarcely noticeable, and are neither invited to come nor received with honour when they come of their own accord, nor are they welcomed with any delight by those whom they visit, who mix them up with their lives and fill up empty spaces with them, like an amusing farce in the intervals of serious business. Let them no longer, then, join incongruous matters together, or connect pleasure with virtue, a mistake whereby they court the worst of men. The reckless profligate, always in liquor and belching out the fumes of wine, believes that he lives with virtue, because he knows that he lives with pleasure, for he hears it said that pleasure cannot exist apart from virtue; consequently he dubs his vices with the title of wisdom and parades all that he ought to conceal. So, men are not encouraged by Epicurus to run riot, but the vicious hide their excesses in the lap of philosophy, and flock to the schools in which they hear the praises of pleasure. They do not consider how sober and temperate—for so, by Hercules, I believe it to be—that “pleasure” of Epicurus is, but they rush at his mere name, seeking to obtain some protection and cloak for their vices. They lose, therefore, the one virtue which their evil life possessed, that of being ashamed of doing wrong: for they praise what they used to blush at, and boast of their vices. Thus modesty can never reassert itself, when shameful idleness is dignified with an honourable name. The reason why that praise which your school lavishes upon pleasure is so hurtful, is because the honourable part of its teaching passes unnoticed, but the degrading part is seen by all.