Has Rupert Murdoch finally said something we can all agree with? Scientology is a "very weird cult" he opined in a tweet at the weekend, "but big, big money involved" He added that there was "something creepy, maybe even evil, about these people". That some of these same criticisms might be levelled at News Corp doesn't negate the fact that the Church of Scientology has a decidedly dodgy public reputation.

Ever since the news broke that Katie Holmes was filing for divorce from Tom Cruise, one of Scientology's most high-profile adherents, commentators have been queueing up to implicate the religion as a source of marital disharmony - or else as a malign influence from which Holmes is trying to escape or to protect her daughter. When it was claimed that Holmes was being followed by men in unidentified cars, the obvious inference was that the Church of Scientology was keeping her under observation or trying to intimidate her. The Church denies this. But the very fact that such a thing could widely be believed points to the organisation's continuing image problem, something that neither its wealth, nor its notorious enthusiasm for litigation, nor its roll-call of Hollywood supporters, have been able to dispel.

In 1985, Mr Justice Latey described Scientology in the High Court as "corrupt, sinister and dangerous", an organisation that "has as its real objective money and power" and called its central technique, known as auditing, a "process of conditioning, brainwashing and indoctrination". The German government in 2008 restricted Tom Cruise's filming in the country on the grounds that Scientology's "totalitarian structure and methods may pose a risk to Germany's democratic society". The organisation has been criticised for secrecy and for financially exploiting adherents. It's regularly claimed that the founder of Scientology, L. Ron Hubbard, created the religion as a money-making scam.

Criticism of the Church's behaviour often goes hand in hand with ridicule of Scientological beliefs and practices. To an outsider, these are bound to seem a trifle eccentric. An important character in Scientology, for example, is said to be a "space lord" named Xenu who brought several billion people to earth 75 million years ago, only to blow them up. The remnants of these immolated souls survived to contaminate the planet. To free people from their negative influence is said to be the main business of Scientology.

It may not help that before he became a prophet Hubbard earned his money writing bad science fiction.

To put this superficially weird mythology in some kind of context, Scientology is the most prominent of a group of new religions that emerged in the second half of the Twentieth century. These creeds blended popular belief in UFOs, speculative science and ideas about the nature of human psychology. Along with Raelianism, the Atherius Society and other, even obscurer, doctrines, Scientology replaced traditional conceptions of God with tales of super-intelligent and technologically superior aliens. As the name "Scientology" itself implies, the intention was to blend science and religion: to make science religious and religion scientific. In Scientology, psychological development is identical to spiritual development. The imagery may derive from sci-fi but behind it is the age-old religious quest for redemption and the secrets of the universe.

To its critics, Scientology looks like both pseudoscience and pseudo-religion. But then most religions require of their adherents belief in concepts or entities that strike outsiders as unlikely or even absurd: Virgin Births, the revelation of scripture by divine dictation, miracles, angels and demons. Is Xenu any more ridiculous an idea than a saviour who could walk on water, or less historical than Abraham? Scientology's credibility problem may partly be a consequence of its youth. It has yet to build up a patina of ancient wisdom, the respectability that comes from age. Nor does it have the ballast provided by a long-standing intellectual tradition.

Otto von Bismarck is reputed to have said that with laws, as with sausages, it is better not to observe them being made. The remark applies, even more strongly, to religion. Unlike in the case of Christianity or even Islam, all too much is known about the founder of Scientology, and much of it is not flattering. This makes it a soft target. Mormonism, too, has to contend with embarrassing details about its founder's biography and doctrines that seem outlandish to outsiders. But it is older than Hubbard's religion by more than a century, even wealthier and much better established. It may soon produce a US president. Although it is not there yet, it is further along the road to "great religion" status and the respectability that comes with that.

New religions can't count on the taboo against criticising other people's deeply-held beliefs that protects older faiths. Beliefs that are unconventional invite mockery rather than respect. That doesn't necessarily mean that Scientology deserves greater respect. It could equally well mean that other religions deserve less. But I find it hard to believe that Scientology is no more than a con-trick. Whatever criticisms may be levelled at the Church of Scientology as an organisation, many people, including highly successful individuals like Tom Cruise, find psychological and spiritual benefit in practising their faith. It obviously works for him. The true test of a religion is not whether its doctrines are plausible but whether it provides a programme for life.