Ethics, is referred to as a concern to act rightly and to live a good life, is pervasive in Plato's work, and so we find Plato's ethical thinking throughout the dialogues. The article discusses the idea of ethics as propounded by Plato. Why does Plato take most people to be drastically wrong about goodness but not about happiness? The answer here lies in the notion of happiness, which is how we have hitherto rendered eudaimonia. Plato's ethical thought is, then, structured by a broad eudaimonist assumption. His main concern is to challenge the views most people have about goodness, for it is here that they go disastrously wrong in trying to live happy lives. Most people think that virtue is a minor good, or even an impediment to living a happy life. Plato considers this to be utterly incorrect; it is only by being virtuous that we can hope to be happy.