Are you are Christian? No, I mean a real Christian.

Can you tell me which is the 34th book of the Old Testament? Are you able to recite the full text of the Niceno-Constantinopolitan Creed? Do you assent to all of the 39 articles? If the answer in any of these instances is no, I regret to inform you that you are clearly not the real deal and should stop pretending otherwise.

I satirise, but only for effect.

Research for the newly-formed Richard Dawkins Foundation for Science and Reason has revealed (drum role) that not all UK Christians are really Christian.

The study, conducted by Ipsos/ MORI found that fewer than three in 10 (28%) people who called themselves Christian in the 2011 Census say they are so "because they believe in the teachings of Christianity", and only half have attended a church service (outside special occasions) in the previous 12 months.

In other words, there are a lot of nominal Christians in Britain. Who would have thought it?

The research itself is massive and fascinating, for which we owe Professor Dawkins much thanks, but it is far from a clear-cut. For example, many people might be surprised to hear that 44% of 'Census Christians' believe that Jesus was "the Son of God, the Saviour of Mankind", that a third believe he was physically resurrected, and that four in ten have read the Bible, independently and from personal choice, in the last a year?

Specific findings aside, however, the business of pronouncing who is and who is not a 'real' Christian is a hazardous one. The Dawkins' press release pushes strongly the idea belief and practice are the only reliable criteria for determining the validity of an individual's faith. However, while there is little doubt that those who believe little, do nothing and know even less about the religion they profess are not really very religious (a very small number, it should be stressed), it is doubtful whether the other element, what you choose to call yourself, is as insignificant as all that.

A number of years ago now, I conducted a series of in-depth interviews with people who did not practice the Christian faith and, as it turned out, knew precious little about it. In other words, the respondents all fell into Dawkins 'not real' category.

Half of them, however, had ticked the Christian box in the 2001 Census, while the other half had not - and the difference was palpable. The former group were vague and hesitant about their beliefs but nonetheless genuinely sympathetic and supportive towards Christianity. By contrast, the latter were angry to point of venomous in their criticisms of it. In other words, nominal attachment did not mean everything but it certainly meant something.

We should bear this in mind when we seek to pronounce on how many real Christians there are in Britain, advice that, incidentally, applies just as much to Christians who try to inflate the figure and its significance just as much as atheists who try to minimise it.

Ironically, given the context of this particular news story, one of the major themes of the gospels is Jesus' running battle with the Pharisees, as they diligently policed the national, religious boundaries, casting out all those who worked on the Sabbath, disobeyed laws on cleanliness and were generally not as punctilious as themselves in obeying the law.

The fact that Jesus redrew the lines so as to include those left out in the cold, and cast out those who judged themselves safely pious and incensed the Pharisees serves as a salutary warning. We should be very careful before we pronounce on who is, and who isn't, the real thing.

Follow Nick Spencer on Twitter: www.twitter.com/theosnick