What does it take to be a Christian?

The Society for Christian Philosophers is open to "anyone interested in philosophy who considers himself or herself a Christian". This always seemed to me to make sense, but I recently got thinking about this as a result of the presentation of data by the Richard Dawkins Foundation for Reason and Science (UK) Religious and Social Attitudes of UK Christians in 2011. This survey, based on 1,136 respondents who said they were Christians showed surprising results: only 32 % of respondents said to believe in the physical resurrection of Jesus (a further 39 % believed in a spiritual resurrection; 44% believed that Jesus is the Son of God. 49 % did not attend religious services, except weddings, funerals and baptisms. Only 35 % knew that Matthew is the first book of the New Testament. Richard Dawkins thinks these data strongly question the place of Christian practices in British societies such as faith schools and bishops in the house of lords, because a large majority of the respondents "are not really Christian at all", but merely "tick the Christian box". 

So does not having the orthodox beliefs and relevant practices mean that people are not Christians? Or is religion such that if one self-identifies as x, one is x, even if one (to take a limiting case) does not observe *any* of the practices or fails to uphold *any* doctrines?

To see the plausibility of this, take an exotic example. My father was born in Malaysia, a multi-cultural but Muslim country, and grew up in a small Roman Catholic community of fishermen. He strongly self-identifies as a Roman Catholic (not just a Christian!) even though he does not believe in the infallibility of the pope, the virginity of Mary, or even the resurrection of the dead. But he is not in the least troubled by this, because to him "religion is a social thing" - it's something that puts Kristangs apart from Muslims, Buddhists and Hindus. For other religions, like Judaism mere self-identification on the basis of the fact that one was raised in the tradition doesn't sound so implausible either (whereas RD did find it problematic that people self-identified as Christians on this basis). 

Recently, cognitive scientist Justin Barrett told me that he does not believe there is such a thing like Christianity, or Hinduism or Islam. (I'm quoting from memory): according to me (and other cognitive scientists of religion) there's no such things as Christianity, but there are Christians. People who self-identify as Christian will have beliefs (private representations) that overlap to some extent, but not completely. And such private representations have priority over public representations, like religious tracts etc. To understand how religion spreads and gets maintained in a population, we should look at the private representations, not the public ones. Perhaps in such a view, mere self-identification is enough to say that someone is a Christian. Indeed, Mountford interviewed quite some people who did not believe in God but self-identified as Christians, going to church regularly. So it should not be so surprising that a minority of respondents in the Dawkins survey (6%) did not even believe in God. 

In a by now viral part of an interview, Dawkins failed to recall the full title of On the Origin of Species, see min. 3.20 - 3.40. This strikes many people as funny, but of course, no one would deny that Dawkins has a profound understanding of evolutionary theory. I know a lot of people who self-identify as atheists and who say that they "believe in evolution". But when you then probe their knowledge of evolutionary biology, you hear the most surprising teleological views. Evolutionary theory is very difficult. Should we conclude on the basis of this that these people do not really endorse evolution? (I find the wording "believe in evolution" quite unfortunate, but this is how I've heard the term used). There might be a disanalogy here: whereas religious affiliation cannot be determined on the basis of a pop quiz, endorsement of a scientific theory perhaps can. Perhaps those who say they believe in evolution without understanding it, merely "quasi-believe" it (to use Sperber's terms).