When I finally read all the way through Mere Christianity for the first time last year, I recall being particularly struck by C. S. Lewis' brief description of what he imagines a properly Christian society would look like. It doesn't match the categories used commonly in contemporary American socio-political discourse, but, man, does it strike just the right notes. First, he lays out some basic principles about what Christianity does and does not mean for the life of society, the polis, i.e. politics. (Note: Though often suspected of being insufficiently Protestant, readers familiar with classical Protestant political theology will actually find very many resemblances here). To start:

…Christianity has not, and does not profess to have, a detailed political program…It could not have. It is meant for all men at all times and the particular program which suited one place or time would not suit another. And, anyhow, that is not how Christianity works. When it tells you to feed the hungry it does not give you lessons in cookery. When it tells you to read the Scriptures it does not give you lessons in Hebrew and Greek, or even in English grammar. It was never intended to replace or supersede the ordinary human arts and sciences: it is rather a director which will set them all to the right jobs, and a source of energy which will give them all new life, if only they will put themselves at its disposal.

Among the first principles, then, is that Christianity provides no comprehensive political blueprint. In contrast to the theonomists or some naive readers of the New Testament, you can't easily lift policies and programs from the pages of Scripture that you can then apply to our own society. There is no need for this. The workings of a society, what we call politics, is a natural art and science. In this sense there is no more such a thing as "Christian politics" than "Christian mathematics," "Christian chemistry," or "Christian programming." What we learn from Christianity is the full and complete picture of what mankind is, is for, and is going, a vision which can then be used to set everything else into the right use and order.

Next, he takes up the question of whether the Church should lead the way in socio-political developments, proclaiming the ideas and visions which society ought to follow. Lewis says that this is true if we consider the Church in its organic form as all believers, so that competent Christian economists and statesmen ought to be leading their fields in the right direction. But he denies as ridiculous the notion that institutional Church, the pastors and bishops and the like who administrate ecclesiastical affairs and relations, should be publishing formal instructions on political concerns. Their job, Lewis points out, primarily respects heavenly and eternal reality: teaching God's Word, administering the sacraments, helping us follow Christ. To make them political thought leaders is to take them out of their field entirely into subjects where they are generally not trained or equipped. The real work is on the laity:

The application of Christian principles, say, to trade unionism or education, must come from Christian trade unionists and Christian schoolmasters: just as Christian literature comes from Christian novelists and dramatists―not from the bench of bishops getting together and trying to write plays and novels in their spare time.

Finally, these formal principles out of the way, Lewis moves on to imagine just what a genuinely Christian society might look like. It's not quite what religious politicians on the Left or the Right today ask for, and I think it brings helpful challenges to both. This section I will simply quote at length, with only a tangential section removed, and it should speak for itself:

Perhaps [the New Testament] gives us more than we can take. It tells us that there are to be no passengers or parasites: if man does not work, he ought not to eat. Every one is to work with his own hands, and what is more, every one’s work is to produce something good: there will be no manufacture of silly luxuries and then of sillier advertisements to persuade us to buy them. And there is to be no ‛swank’ or ‛side,’ no putting on airs. To that extent a Christian society would be what we now call Leftist.

On the other hand, it is always insisting on obedience―obedience (and outward marks of respect) from all of us to properly appointed magistrates, from children to parents, and (I am afraid this is going to be very unpopular) from wives to husbands. Thirdly, it is to be a cheerful society: full of singing and rejoicing, and regarding worry or anxiety as wrong. Courtesy is one of the Christian virtues; and the New Testament hates what it calls ‘busybodies.’

…Now another point. There is one bit of advice given to us by the ancient heathen Greeks, and by the Jews in the Old Testament, and by the great Christian teachers of the Middle Ages, which the modern economic system has completely disobeyed. All these people told us not to lend money at interest: and lending money at interest―what we call investment―is the basis of our whole system. Now it may not absolutely follow that we are wrong. Some people say that when Moses and Aristotle and the Christians agreed in forbidding interest (or ‘usury’ as they called it), they could not foresee the joint stock company, and were only thinking of the private moneylender, and that, therefore, we need not bother about what they said. That is a question I cannot decide on. I am not an economist and I simply do not know whether the investment system is responsible for the state we are in or not. This is where we want the Christian economist. But I should not have been honest if I had not told you that three great civilisations had agreed (or so it seems at first sight) in condemning the very thing on which we have based our whole life.

One more point and I am done. In the passage where the New Testament says that every one must work, it gives as a reason ‘in order that he may have something to give to those in need.’ Charity―giving to the poor―is an essential part of Christian morality: in the frightening parable of the sheep and the goats it seems to be the point on which everything turns. Some people nowadays say that charity ought to be unnecessary and that instead of giving to the poor we ought to be producing a society in which there were no poor to give to. They may be quite right in saying that we ought to produce this kind of society. But if anyone thinks that, as a consequence, you can stop giving in the meantime, then he has parted company with all Christian morality. I do not believe one can settle how much we ought to give. I am afraid the only safe rule is to give more than we can spare. In other words, if our expenditure on comforts, luxuries, amusements, etc., is up to the standard common among those with the same income as our own, we are probably giving away too little. If our charities do not at all pinch or hamper us, I should say they are too small. There ought to be things we should like to do and cannot do because our charities expenditure excludes them. I am speaking now of ‘charities’ in the common way. Particular cases of distress among your own relatives, friends, neighbours or employees, which God, as it were, forces upon your notice, may demand much more: even to the crippling and endangering of your own position. For many of us the great obstacle to charity lies not in our luxurious living or desire for more money, but in our fear―fear of insecurity. This must often be recognised as a temptation. Sometimes our pride also hinders our charity; we are tempted to spend more than we ought on the showy forms of generosity (tipping, hospitality) and less than we ought on those who really need our help.