Dr Rowan Williams, the Archbishop of Canterbury, has the sort of beard to which we should all aspire. It does not, perhaps, possess the wilful abandon of the Greek Orthodox beard (a church for which he nonetheless has some theological affection), nor the unbending certainty of the fundamentalist Muslim beard.

It is instead a centre-left, progressive, Church of England beard, a beard with its historical roots in Fabianism but tempered by modernity. When Williams was jostling for position to succeed George Carey, his beard marked him out as a thinker, which was what we wanted after the guileless, low church evangelism of his predecessor. Rowan got the job.

Last week he and his beard have been once again addressing the issues of globalisation and Third World debt.

A disaffection for both is a prerequisite for the wearer of a centre-left progressive beard. In a sermon to mark the 60th anniversary of Christian Aid, Williams attacked the "naive" belief in free trade that contributes to the impoverishment (fiscal rather than spiritual) of developing countries. He illustrated his sermon with Paul's letter to the Corinthians - that's St Paul, I assume, rather than, say, Paul Wolfowitz. I don't think he has ever written to the Corinthians.

Williams has been here before. A few years ago he harangued a bunch of British businessmen with a thesis drawn from a couple of articles he had read in the New Statesman.

"We have begun to wake up to the cyclical nature of the deprivation produced by international debt," he announced, proceeding to develop a critique that you will have heard more recently from a variety of international debt experts and theologians such as Bono, Sir Bob Geldof and Richard Curtis, creator of The Vicar of Dibley.

Williams conceded that there were flaws in the arguments of the more extreme anti-globalisation protesters: the West was not entirely to blame for the mess within which Africa perennially finds itself - but nobody "should be allowed to suppose that the wealthy nations and their financial institutions (including the World Bank and the IMF) are without responsibility".

This time around, the archbishop's sermon concerned itself primarily with the issue of trust and "the scandal of a global economy that leaves children dying and billions in extreme need".

Central to his thesis was the following, one supposes rhetorical, question: "Do we want to live in a world where trust seems natural?" Or, as a corollary, one in which "rivalry or mutual isolation are the obvious forms of behaviour?"

This is philosophical deep water, even for someone with a quite impeccable, top-of-the-range beard. We might reply simply by saying: "Yes, I'd rather live in a world where we all trust each other purely as a matter of course, rather than through a social contract formed by commonly assumed reciprocity of actions. However, beardo, that's the way it is, unfortunately."

We might also question quite what Rowan means by his deployment of the word "natural". Trust, like altruism, is wholly natural when it confers a reciprocal advantage. The problem with his rhetorical question is that the two states he identifies as antithetical are, in fact, not so at all.

Indeed, trust occurs precisely because we live in a world characterised by rivalry and mutual isolation. Therefore we need to construct an appropriate mechanism for ensuring co-operation. This may be a bleak view of the human condition - but simply because something isn't very nice does not mean that it isn't correct.

Thus it is with Third World debt. Like it or not, countries that reschedule and reschedule their debt burden, or have vast chunks of it written off, will find their credit ratings taking a hit. It is an inescapable effect of that thing we call trust or, rather, in this case, a profound lack of it. And it is why many Third World countries, such as Laos, resist such easy temptations. It is also why other Third World countries that are diligently paying off their debts and thus improving their economies get very angry when rival states are suddenly given a free ride because of their utter incompetence. Trust cannot be conferred upon an individual, or a country, simply because we have an insuperable desire to make the world a nicer place. If we were to do that the whole concept of trust would lose its meaning.

Similarly, the notion that we might eliminate Third World impoverishment simply by bunging vast amounts of money the way of, say, Somalia or Sudan is, these days, almost universally derided. There is a growing body of opinion which holds that aid has actually worsened the plight of Africa, encouraged misrule and led to economic collapse and civil conflict.

As Michael Edwards of the World Bank once put it: "Africa's crisis is one of governance."

Too often aid sustains regimes that are corrupt, violent, staggeringly useless or, usually, all three. Too often aid is used to finance opportunistic territorial wars against similarly corrupt and useless countries.

The recent 20th anniversary of Live Aid should have provoked us to examine precisely how the Ethiopian government behaved once Geldof and his friends had bunged in all that cash: repression, border wars, corruption, civil war. Instead we wrung our hands, noted that Ethiopia was actually worse off than it was 20 years back and insisted that more money be poured into that benighted country.

In other words, we reached for the easy answer - that Ethiopia's plight was not a result of human wickedness, untrustworthiness or stupidity, but a sort of act of God aided and abetted by the perfidiousness of the affluent West. Whereas, in reality, it is a result of very bad governance aided and abetted by the mindless magnanimity of the affluent West.

Williams is right - trust is the key to solving the problem of Third World debt. You may even, if you wish, concur with him that trust is a God-given quality. But either way it is a contingent commodity and cannot exist in a vacuum nor be artificially imposed.

When we look at Africa, and at our undoubted affluence, our conscience pricks us and we reach for the closest thing to hand to salve the wound - our money.

I would be interested to hear a Christian leader contemplate that this is altogether too glib and easy a solution.

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