An icon is someone you can recognise from behind. William Hague and Kate Winslet, for example, are not icons; Margaret Thatcher and John Wayne certainly were. And two of the greatest extant icons came together this week on a warm, beautiful island in the Caribbean.

No, not Mick Jagger and Tina Turner on Mustique. Two great hero/villains of the second half of this century, celebrated their likely survival into the early years of the next, by meeting up, kissing each other and hanging out. The Pope and Fidel (having outlived Leonid, Margaret, Josip Broz, Kim Il Sung and Jimmy Stewart) were celebrating their own remarkable longevity. To see them together was to go on icon overload, like looking at old photographs of Churchill, Stalin and Roosevelt at the Yalta conference, or a enjoying a dream of Diana having dinner with Marilyn in heaven.

For one moment I had a fantasy of them swapping their iconic togs, like footballers exchange shirts at the end of a big match. Fidel would clamber into a cassock, hang the crucifix round his neck and don the skullcap. John Paul II, in turn, would fasten those fatigues, pull up the combat boots and firmly clamp a huge Havana between his dentures. Disappointingly, only one wore the full iconic regalia: the Pope turned out in snow-white Popegear, but Castro wore a dark suit. This made him look attractively winsome, as though he were a young suitor visiting his girlfriend's parents one Sunday lunchtime.

So, there they were, these two redoubtable men, icons grown old. One once represented the vigour, sexiness and hope of socialist revolution; the other the much longer tradition of the one true church. What was it that drew them together, that made their sharing of one spotlight so surprisingly comfortable?

There is, after all, one pretty bone of contention between them - God. Fidel does not believe in him, and the Pope does. And, insofar as communism has traditionally been associated with godlessness, one would expect the Cuban regime to be exactly the type of government here on earth that the Pontiff would most like to dislodge. Especially as he has been accorded a similar accolade with regard to the fall of the Berlin wall to that which The Sun allowed itself after the 1992 election - it was the Pope wot won it.

It should not have been a surprise, therefore, to see the American magazine Time comment in its latest issue that "this week the Pope brings his message of freedom to Fidel Castro, as two of the world's giants collide". According to this version of the iconoclash, Fidel is tolerating the Pope because he is desperate for recognition, and the Holy Father is there to wean weary Cubans away from communism.

This is old-fashioned, America-centric, Cold War bollocks. The idea that the Pope has a "message of freedom" is in any case bizarre. Catholicism is not about freedom, which it does not recognise as essential for the human condition. Dignity, yes. Freedom, no. The Holy Office of the Inquisition - renamed the Congregation for the Doctrine of the Faith - still exists today; and you can still be branded a heretic in today's church. Old Galileo was only rehabilitated in 1992, some 360 years after having been condemned; Gorbachev managed to get Bukharin rehabilitated inside 50.

But even the fact that both Cuba and the church aren't democratic isn't really the point. The fact is that, these days, there is more that can unite men like Castro and Wojtila than must necessarily divide them. For a start, they are not as hostile to each other as an American perspective might assume. Fidel has drunk at the well of liberation theology; there are plenty of Catholics that he likes and would call comrade. His enemies are those forces that would crush him and - in his terms - destroy his country. Catholicism is not one of those forces.

Now look at the world from under the skullcap. communism, once the terrible secular threat to organised religion, is everywhere vanquished. From Italy to Argentina, from Canada to Kamchatka, there are no communists. Across the world the market reigns. So the Pope's enemy is no longer organised labour, marching to the drumbeat of a single ideology, defeated if that one ideology is defeated. In 1998 it is the far more powerful, less ideological and therefore less confrontable global system of capitalism which provides the church with its challenge.

In its global phase capitalism is raising as many ethical and spiritual questions, as it answers material ones. Across the developed world many are richer, but most are, they say, no happier. In a flicker of a computer screen whole communities are swept away, employers feel no responsibility for their employees, employees feel no loyalty to their companies. Fidel and John Paul may look at Russia, and see communism replaced with prostitution, exploitation, rampant crime and all the other ugly stepsisters of consumerism. And both do not like what they see. This is something that Americans cannot understand.

So, these two last doddering representatives of two great ideologies, both of which contend that there is something above us, whether it be the possibility of a heaven on earth, or the certainty of a heaven in heaven, can find both common cause and sense some opportunity. Both members of a priestly caste, set to show us the path to enlightenment, they appeal, in their different ways, to deeper human values. They can make us good human beings. Anything you can do, they are saying, icon do better.