Many people know Paul Kennedy as the author of the bestselling The Rise and Fall of the Great Powers . Now, thanks to a poignant opinion piece in The New York Times , everyone knows he is a Catholic. He notes with irony that he is probably the only known practising Catholic professor at the very liberal Yale University. Published to coincide with the pope's resignation this week, his opinion-page article caught my attention because he said in the first paragraph he had been baptised at the age of two weeks - about the same age at which I was baptised. Wikipedia says he is 66, so he has kept the faith all that time. I lost mine within 20 years. Strangely, the article has almost nothing to say about the pope. Perhaps Benedict is old news. What Kennedy does try to say is something more timeless: what it means to follow Christ. But he also takes on the anti-Catholic critics who just don't get it. All the criticism - about paedophile priests, sex abuse, financial irregularities, against gay marriage, use of contraceptives and women priests, etc - are sideshows, "footnotes" he calls them, compared with Christ's message, which is: to love a stranger, "your unknown neighbour", as yourself. That may be so. Kennedy is probably right about Christ. Who are we non-Christians to argue with him anyway? But what about those sideshows? That's the problem with his article. Fine, he wants to talk about the eternal church, the one that lives in a Christian's heart. But when you have more than one billion followers on Planet Earth, you do need what he calls "a worldwide church structure". This is the church of this world, of bureaucracy, money and influence, power struggles and abuses, of scandals and cover-ups. Few people have had to live more acutely with this elemental conflict between the eternal and the temporal, the holy and the ugly, than Benedict. By all accounts one of the world's great theologians, he was also the head of the Congregation for the Doctrine of the Faith, formerly called the Inquisition, after he became a cardinal. A long list of alleged cover-ups and conspiracies involving paedophile priests on four continents flowed from his office. That is a terrible burden compared with the pure life of the mind he now seeks.