For Plato, ethics is not about rules or consequences—it's about becoming a certain kind of person. Virtue (arete) is excellence of the soul. A virtuous person has a well-ordered soul where reason rules. This makes them truly happy (eudaimonia), regardless of external circumstances.
The Four Cardinal Virtues
1. Wisdom (sophia)
The virtue of the rational part. Knowledge of what is truly good. The philosopher's virtue. In the state: possessed by philosopher-rulers.
2. Courage (andreia)
The virtue of the spirited part. Steadfastness in danger. Knowing what to fear and what not to fear. The guardian's virtue. In the state: possessed by the warrior class.
3. Temperance (sophrosyne)
The virtue of the appetitive part (when controlled). Moderation, self-control. Agreement that reason should rule. In the state: possessed by all classes when each accepts its role.
4. Justice (dikaiosyne)
The harmony of the whole. Each part doing its proper function. The master virtue. In the state: each class performing its role without interfering with others.
The Unity of Virtue
Plato held a controversial view: all virtues are ultimately one. True wisdom includes knowing what to fear (courage), knowing when to restrain desires (temperance), and knowing what belongs to each part (justice). You cannot have one virtue without the others.
This "unity of virtue" thesis means: there are no brave fools, no temperate cowards, no wise but unjust people. Genuine virtue requires complete understanding of the Good.
Virtue as Knowledge
Socrates' most famous claim, adopted by Plato: virtue is knowledge. No one does wrong willingly. If you truly know what is good, you will do it. Vice is ignorance.
This seems counter-intuitive. Don't people knowingly do wrong? Plato's response: they think the wrong action is good (pleasant, profitable, etc.). If they truly knew the ultimate Good, they couldn't choose evil.
"No one who knows or believes there is something else better than what he's doing, something possible, will go on doing what he had been doing when he could be doing what's better."
—Plato, Protagoras 358b-c
Virtue and Happiness
Plato argues virtue guarantees happiness. The virtuous soul is healthy, harmonious, beautiful. The vicious soul is sick, chaotic, ugly. Would you trade health for pleasure if it meant disease? No. Similarly, you shouldn't trade virtue for external goods.
The tyrant—who has everything external yet whose soul is enslaved by appetite—is the most miserable person. The philosopher—who may have nothing external yet whose soul is well-ordered—is happiest.
Justice is Profitable
Plato's central argument in the Republic: justice is profitable. Not because it leads to rewards (though it may), but because justice is the health of the soul. An unjust soul is disordered, and disorder is painful.
Would you rather be unjust but appear just, or just but appear unjust? Plato argues: just but appearing unjust. The internal state matters more than reputation.
Modern Questions
- Is virtue really knowledge? Can't we know the good yet fail to do it (weakness of will)?
- Is virtue really sufficient for happiness? What about someone virtuous but tortured?
- Are the four virtues really unified? Can't someone be brave but unwise?
- Is Plato's psychology accurate? Is the soul really tripartite?
Despite these questions, Plato's virtue ethics influenced all subsequent ethics. The idea that character matters more than actions, that flourishing requires excellence, remains powerful.