Argue with Christians (Hi there, Jim! Hi there, Don!) about the veracity of their faith and they will tell you it’s true for two reasons: the Bible and their own personal experience. ‘Christianity is true and Jesus is real because the Bible says so – and, whatsmore, I feel it.’

Or, as William Craig Lane likes to put it, the inner witness of the Holy Spirit testifies to the truth of Christianity. It’s a beautifully circular argument: ‘Christianity and its holy book are true; I know this because the Holy Spirit who lives in me tells me so; I know the Holy Spirit lives in me because the Bible says he does; therefore, I know Christianity and the Bible are true because the Holy Spirit tells me so’.

But equally, Mormons claim that they ‘know’ a completely different set of improbable beliefs are true because they experience a ‘burning in the bosom’ that tells them so. Roman Catholics say their faith is true because they experience Christ through the Eucharist, while Muslims know theirs is true because they have a real sense of Allah’s presence.

All of these spiritual convictions are not, as a liberal theologian like Karen Armstrong might claim, evidence that there is Something-Out-There that loves and communicates with us, but more obviously that human beings’ brains are adept at creating whatever ‘inner witness’ is required to support the beliefs and convictions they have arrived at. William Lane Craig concedes this when he acknowledges that

Anyone (or, at least any sort of theist) can claim to have a self-authenticating witness of God to the truth of his religion. But the reason you argue with them is because they really don’t: either they’ve just had some emotional experience or else they’ve misinterpreted their religious experience.

In other words, any experience of ‘self-authenticating witness’ enjoyed by believers in faiths outside Craig’s own brand of Christianity is at best mistaken, at worst fake. But then, how can anyone know, Craig included, that his own conviction isn’t just as much an emotional flush or mere subjective experience? Why is his conviction any more real than that of other kinds of believers? Ultimately, Craig can only say, “because it is”:

a person (possessed by the Holy Spirit) does not need supplementary arguments or evidence in order to know and to know with confidence that he is in fact experiencing the Spirit of God.

In other words, the true believer knows his experience of the Holy Spirit is real because his experience of the Holy Spirit tells him it is. And round the argument goes, though no amount of assertion makes a subjective experience an event in objective reality.

It is impossible for Craig, or any other Christian, to demonstrate that an entity he imagines inhabits his brain, no matter how convincing its presence may seem, has any existence anywhere other than in his brain. What the person who says ‘I believe’ is really saying is that they have no evidence at all for what they are claiming. If they had, they wouldn’t need to believe it; they would know it. They would, whatsmore, be able to point to independent, external evidence for it.

The Bible makes a virtue out of not knowing, of believing when there is no evidence.  It calls the resulting cognitive dissonance, ‘faith’.

Adapted from my book, Why Chrisitans Don’t Do What Jesus Tells Them To …And What They Believe Instead.