In the great culture war between atheists and the faithful, it is all too easy to miss issues of common interest. One such issue – of the greatest urgency – is the contemporary assault upon truth, and the rise of the “post-truth” era. What the faithful and what non-believers mean by “truth” diverges radically once the question of the metaphysical is reached. But there is (or should be) a shared commitment to the core concept itself: the notion of veracity and, correspondingly, of falsehood.

Post-truth is not, as is sometimes assumed, just a newly fashionable description of lies, spin or disinformation. It describes a more complex phenomenon, in which emotional resonance is becoming more important than facts and evidence, and verification is being replaced by social media algorithms that tell us what we want to hear.

When Kellyanne Conway, a senior aide to Donald Trump, spoke of “alternative facts”, she described a new epistemology in which you choose your own reality, as if from a buffet. Last December, an Ipsos poll of more than 3,000 Americans found that 75 per cent of those who saw fake news headlines believed them to be accurate.