Letter 92 (§23)

“Then if, as you say, the wise man cannot fall from happiness to wretchedness, he cannot fall into non-happiness. For how, if one has begun to slip, can one stop at any particular place? That which prevents him from rolling to the bottom, keeps him at the summit. Why, you urge, may not a happy life possibly be destroyed? It cannot even be disjointed; and for that reason virtue is itself of itself sufficient for the happy life.”