There is no single practice or belief which is always and only religious. Neither is there any guarantee that "religious" ideas have anything in common with each other - not even that they can all grow in the fertile mulch that lines the skull of a football manager. Yet the word is a useful one. It does mean something important to say that Europe is entering a post-religious age, though it clearly does not mean that we are entering an age of rationality (or even of unbounded credulity).
One way round the difficulty is to talk about "organised religion" but I think this is just weasel-ish because organisation is one of the defining qualities of a serious religion, without which it cannot long persist. We don't normally talk about "nourishing food" or "mothers with children" - and "organised religion" is a similar tautology.
What makes a religion "organised" is more than simply discipline. The boundary between religions and cults may be obscure, and fuzzy, but it certainly exists. There are cults and sects which are far more ferociously disciplined than traditional forms of Christianity. There are some which seem to have emerged from that state to become full- blown religions: Mormonism comes to mind. But there is movement in both directions, as other fragments of established religions sink into cult- hood, like some of the wackier Pentecostal churchlets, with their belief in divinely inspired leaders.
The definition of a cult seems to have more to do with the relations between the members and the society around them. Sacred cows are part of a religion in Uttar Pradesh. But when you see them cropping peacefully in the Hertfordshre commuter belt, you know you have found the Hare Krishnas' mansion. Though the movement is organised, and a religion, its distance from most of the surrounding society means that its white members certainly are practising what we might call disorganised religion. Sometimes, of course, this transfer into a foreign society can render a religion more rather than less benevolent. The heart sinks a little at Ian Paisley's missionary journeys in West Africa or Wales, but at least his followers do less harm there than in Northern Ireland.
If I am right, and Paisleyism in Cameroon is a cult of sorts, whereas in Northern Ireland it is a religion or part of one, this shows at least that religions are not necessarily more benificent, still less benevolent than cults. But there is one form of organisation of which only religions are capable. It combines discipline, organisation and a healthy relationship with the surrounding society. The fact that it no longer happens in Europe summons up exactly what is meant by secularisation. The golden test is this: proper religions can found universities.
By this token, European Christianity, Buddhism, Islam, Judaism, Confucianism and possibly Hinduism are certainly religions. I know there are American fundamentalist universities. Ian Paisley got his doctorate from one, but that's not the only reason for distrusting them. The US also have a University of the Hamburger, and I don't think that's part of a religion either. A proper university cannot be fundamentalist, since fundamentalism is a 19th-century reaction to the discovery that knowledge and religious truth may be incompatible. A real university can't be so afraid that it can only go out into the world wearing blinkers. A friend of mine taught for a while at an Islamic University in Malaysia, and found the experience completely stultifying simply because everything thought or taught had to be checked to see if it drifted into for- bidden territories.
Religions need more than unself-conscious intellectual confidence if they are to launch universities. They need money; libraries and learning have always been expensive, even if scholars are cheap. And they need the confidence of the society surrounding them. A university is not a vocational college. It's not even a seminary. It is something which is recognised to benefit the whole of the society surrounding it. All of these are resources which are beyond cults, almost by definition. They are certainly beyond disorganised spirituality. A university of the New Age would be as much use as a Hamburger University, even if there were anything solid to study there.
The links between Western European Christianity and the universities have collapsed almost completely: I think that Cardinal Newman was the last man to attempt to found a religious university in these islands, and certainly the idea would never occur to anyone today. This is perhaps the most concrete meaning that can be attached to the idea of a post-religious society. This distinction has the further advantage of holding even in Eastern Europe, where religion is alive partly because its connection with universities remains organic. Which explains why a former Polish university professor like Pope John Paul II, who really believes that a university without religion has lost its soul, thinks in ways which seem so completely alien to most Western intellectuals.