For most Greeks the question, "Why be moral?" is at the heart of morality. According to Greek morality, the individual should be moral because of the good it yields. With Socrates and Plato however, the focus of the question regarding, 'What is moral?" is shifted. According to Socratic and Platonic ethics if we know what is good that will be enough to indicate why we should act morally.
• Thrasymachus (427 B.C.): He was a Greek sophist and is known mainly as a character in Book I of Plato's "Republic." Thrasymachus traveled and taught extensively throughout the Greek world and was well known in Athens as a teacher and as an author or treatises on rhetoric. According to him, morality encompasses the rules or conventions imposed on others by those in power for their own benefit. Bang immoral is advantageous to me. That is, being immoral does not necessarily make one unhappy.
• Glaucon and Adeimantus: According to these writers being moral is beneficial to the person who is being moral. But if I could be immoral without suffering, I would be a fool not to be immoral (See Gyges ring). Even giving the appearance of morality is better than actually not acting morally.
• Socrates and Plato: The good consequences of being moral are not what makes actions good; rather, actions have good consequences because them are good in themselves and such actions ought to be done for that reason alone. Immorality is due to one's ignorance of the good.
For Plato, the good is defined in terms of balancing elements of the soul. As with society, the soul has three parts: the ruling part, the enforcement part and the productive part.
• The ruling part (rulers are like the soul's reasoning abilities) that knows the truth or essence of what it means to exist in harmony. The virtue of this group is wisdom.
• The enforcement part of the soul is our spirit, drive, or commitment. In society this is represented by the guardians (police, soldiers) that implement philosophical principles, and their virtue is courage.
• The productive part or the gets things done part of the soul (appetite, lusts, and irrational desires) has its parallel in the workers and artisans in society whose virtue is moderation.
Justice occurs when the parts of the soul are in ma=harmony and this means that we act in accord with human reason, doing what is appropriate given our place in society. This is virtue or "arête". For Plato we should be moral because to do so is to be harmoniously integrated with oneself.
