Plato taught that every person wants happiness no matter how wicked they are because whatever they do they do it believing that it will bring them happiness. Of course, Plato did not know psychology, not even as well as the playwrights and historians of his time. By this standard, everyone desires peace of mind, too, because whatever they do they claim it is for their own good.
Happiness or peace or mind: it is the same error, for our desires, our clingings and graspings, are rationalized as necessary to achieve a state of mental satisfaction or, for that matter, happiness. This realization should be a caution to us. The most important mental function we have is to constantly “check in” with ourselves as to why we do things. We must analyze as bluntly as possible whether what we want is realistic, whether what we say (to ourselves and others) is honest. Fortunately, we don’t have to confess or mumble these secrets to anyone, just keep our own watch on our thoughts. This is, after all, what used to be called “examination of conscience” except that now we are not looking for sins but for habits, assumptions, values, emotions, aspirations, and illusions. Plato’s Socrates is right when he calls the contrast an “unexamined life.” We see this lack of self-knowledge everywhere around us. We must hold a mirror to ourselves, polishing it all the time in order to reflect truly what we need to see.