There are, according to Lewis, seven virtues. "Four of them are called 'Cardinal' virtues, and the remaining three are called 'Theological' virtues. The 'Cardinal' ones are those which all civilized people recognise: the 'Theological' are those which, as a rule, only Christians know about."
This chapter, as you can see, deals only with the Cardinal virtues. Lewis says he'll get back to the Theological ones later, and I must believe him. :)
The term 'cardinal' has nothing to do with Cardinals, either the birds or the Roman Catholic ranking of priests. According to Lewis it comes from a Latin word meaning 'the hinge of a door'. I made use of the wonder that is Google and found that the term for the hinge of a door is 'cardin'. So, there you are.
The first Cardinal virtue is prudence. Prudence is, essentially, practical common sense - taking the time to think about what you're doing and what the likely outcome is going to be. Many people think that Christians are supposed to be 'foolish'. They take the instruction to 'be like children' in order to enter Heaven incorrectly. Christ told us "to be not only as 'harmless as doves', but also 'as wise as serpents'. He wants a child's heart, but a grown-up's head. He wants us to be simple, single-minded, affectionate, and teachable, as good children are; but He also wants every bit of intelligence we have to be alert at its job, and in first-class fighting trim."
Lewis believes that being a Christian will keep a person sharp. "Anyone who is honestly trying to be a Christian will soon find his intelligence being sharpened: one of the reasons why it needs no special education to be a Christian is that Christianity is an education itself."
Then why do we have so many classes about Christianity? I don't think this is what he was going for, but Christianity is not instinctive. It's not something where you go, 'Oh, I'll be a Christian' and suddenly you know how. You have to be taught and so, um...yeah. I think being a Christian *does* require a special education. It is also an education unto itself, since you learn the tenets and then have to live them which teaches them to you even better.
The next cardinal virtue is temperance. Most people, as Lewis points out, view temperance as cautioning against excessive drinking. But that's not what it means, really. It refers to *all* pleasures, and it's not about abstinance. It's about *restraint*. You go so far, to a reasonable point, and no further.
"An individual Christian may see fit to five up all sorts of things for special reasons...but the moment he starts saying the things are bad in themselves, or looking down his nose at other people who do use them, he has taken the wrong turning."
Temperance = moderation. It is reasonableness in your actions. Are you unable to drink a little without drinking a lot? Then don't drink. Are you making a hobby the center of your life and neglecting you family or your other responsibilities? Then you need to reduce the level of involvement with that hobby.
The third cardinal virtue is justice. "It is the old name for everything we should now call 'fairness'; it includes honesty, give and take, truthfulness, keeping promises, and all that side of life."
The fourth cardinal virtue is fortitude: "both kinds of courage - the kind that faces danger as well as the kind that 'sticks it' under pain."
So the four cardinal virtues are, in Amber terms: Common Sense, Self Control, Fairplay and Strength of Character. I don't think that very many people would say that any of these are bad things and since these are the virtues that Lewis says everyone is aware of I don't know that there's really anything more to say. We'll see about the theological virtues once we get to those.