The Four Cardinal Virtues
This week you are going to learn about the Four Cardinal Virtues: wisdom, courage, justice, and temperance. "Cardinal" comes from the Latin cardo, meaning hinge. These four are the hinges on which a good life swings. The Stoics inherited them from Plato and Socrates, then sharpened them into something practical: not ideals to admire from a distance, but habits of mind and action you can exercise every single day. By Saturday, you will not just know what they are; you will have a feel for how they work together as one way of living.
Passage
Now let us turn to a consideration of the virtues. Some persons will advise us to rate prudence very high, to cherish bravery, and to cleave more closely, if possible, to justice than to all other qualities. But this will do us no good if we do not know what virtue is, whether it is simple or compound, whether it is one or more than one, whether its parts are separate or interwoven with one another; whether he who has one virtue possesses the other virtues also; and just what are the distinctions between them.
— Seneca, Letters 95.55
Reflection
Seneca raises the stakes today. He says it is not enough to be told to be brave or just; you need to understand what virtue actually is before any of that advice does you any good. Is virtue one thing or many? Are the virtues separable, or do they come as a package? This is not mere philosophy trivia. If virtue is genuinely one, then working on courage is also working on wisdom, and neglecting temperance quietly erodes justice. Seneca is asking you to move from following rules ('be brave') to understanding principles ('here is what virtue is and why it works the way it does'). That shift, from obedience to understanding, is itself an act of wisdom.
Go deeper
In your own experience, when you have genuinely grown in one virtue, did you notice any change in the others, and if so, what did that look like in practice?
Practice
One Question, Held Carefully
Seneca's question today is simply: what is virtue? Do not answer it quickly. Spend five to eight minutes writing your own honest attempt at a definition, in plain words, without quoting anything. Then read it back and ask: does this actually explain anything, or is it just restating the question? If you get stuck, that is the point. Noticing where your understanding runs out is how understanding grows.