Post-truth refers to blatant lies being routine across society, and it means that politicians can lie without condemnation. This is different from the cliché that all politicians lie and make promises they have no intention of keeping — this still expects honesty to be the default position. In a post-truth world, this expectation no longer holds.
This can explain the current political situation in the United States and elsewhere. Public tolerance of inaccurate and undefended allegations, non sequiturs in response to hard questions and outright denials of facts is shockingly high.
More radical forms of relativism are often denounced as undermining basic values. Friedrich Nietzsche, the nineteenth-century philosopher who is often invoked to justify post-truth, was such a relativist, and he does suggest at times that deception is rife and should not be categorically rejected. His point is to complicate our view of human behaviour and to object to moral certainties that encourage black-and-white judgements about what’s good and what’s evil. Thus he denies that there are moral facts, saying that we have only “moral interpretations”, and in doing so denies that moral assertions are unconditionally true. But this does not mean there is no truth. Even when he claims that our truths amount to our “irrefutable errors”, he is pointing to the exaggerated clarity of abstractions by comparison with empirical reality.
In fact — contrary to how he is often presented — Nietzsche held intellectual honesty at a premium. His most strenuous rejections of ‘truth’ are mostly directed not at truth, but at what has been asserted as true. Yes, Nietzsche was an elitist who was sceptical of democracy, and so his work does not necessarily fault leaders for talking down to the public. But it also points out the inconsistency of religious teachers who assume they have the right to lie.
Scientists and philosophers should be shocked by the idea of post-truth, and they should speak up when scientific findings are ignored by those in power or treated as mere matters of faith. Scientists must keep reminding society of the importance of the social mission of science — to provide the best information possible as the basis for public policy. And they should publicly affirm the intellectual virtues that they so effectively model: critical thinking, sustained inquiry and revision of beliefs on the basis of evidence. Another line from Nietzsche is especially pertinent now: “Three cheers for physics! — and even more for the motive that spurs us toward physics — our honesty!”
