'... let us recall the well-known statement of a university professor in the
Republic of the Massagetes: "Not the faculty but His Excellency the General
can properly determine the sum of two and two."'
- Hermann Hesse
The world is a dangerous place right now. Politicians encourage a new version of the Cold War's nuclear arms race, more dangerous now because there are more players in the game. Greed overrides prudence in the rush to burn our last resources of fossil fuels, leading the planet ever closer to an irreversible tipping point of climate change. And relentless human population pressure drives more of our fellow species to extinction.
Those are opinions. But the facts on which they are based are not.
There are two ways to react to the situation. We may wait passively for the Horsemen of the Apocalypse to come and do their work. Or we may put our trust in tried methods of reasoning, observation, and experiment to look for ways to alleviate things.
The fact that two plus two equals four is unlikely to be challenged, even by an all-powerful leader. But this is only the edge of a spectrum that includes much of what we know. Post-modern attempts to relativise truth do not change this. If one person believes that the earth is six thousand years old, while another believes it is four-and-a-half billion years old, they cannot both be right. Nobody who walks along the Fife Coastal Path and sees the Isle of May disappearing below the horizon can believe that the earth is flat, unless they simply refuse to think about it. These things are obvious, but the continuum of observed fact runs directly to the increase in global temperature and the proliferation of nuclear weapons.
"Truth is not disposable, and on the important issues it is not relative"
Of course, mathematicians are at one end of the continuum. Our subject is the most securely founded of any in the academy. Some critics make great sport out of Gödel's famous Incompleteness Theorem, using it to maintain that there is a crisis in the foundations of mathematics. Perhaps unsurprisingly, very few of these critics know exactly what the theorem says, and fewer have read the proof. A mathematical proof is an argument capable of convincing a sceptic of the truth of the proposition being proved. If we did not have a secure proof of Gödel's theorem, there would be nothing to argue about anyway. G. H. Hardy said, "Pure mathematics ... seems to me the rock on which all idealism founders: 317 is a prime, not because we think so, or because our minds are shaped in one way rather than another, but because it is so, because mathematical reality is built that way." This is so obvious that writers of fantasy from Jorge Luis Borges to Russell Hoban have stretched our imaginations by taking us to places where it is not so. But in our world, for better or worse, it is.
The sciences do not have the same level of certainty. Indeed, chaos theory has taught us that the far future is less predictable than we may have hoped. Against that, we can observe the present in far greater detail now than has been possible before, and this allows at least short-term predictions to be reasonably accurate. Also, chaos theory is not going to invalidate the science of climate change – no angel's wing will save us from ourselves. The observations, and the trends predicted from them, are as secure as anything can be in the real world.
The problem here is in making sense of the huge amount of data we now have access to, and extracting meaningful patterns from it. This is why "big data" is such a buzzword now, and this is a challenge we will have to face. The problem then is that the chain of inference from the data to the patterns we extract becomes longer and more tenuous, and so our conclusions are less secure. Rather than give up hope, we have to put more effort into understanding how to use big data to make decisions, rather than just basing them on gut reactions.
Personal beliefs would hardly matter, if it were not for the fact that they lead to actions which affect us all. When His Excellency the General tells the Environmental Protection Agency what results they are not allowed to publish, it should warn us all that we are in trouble, and we had better take a stand. Truth is not disposable, and on the important issues it is not relative.
This issue cuts across the political spectrum, although it does appear at present that "post-truth" is chiefly pushed by the Neoconservatives. Indeed, Alan Sokal was led to his famous hoax in the journal Social Text because of his dismay that the New Left was embracing postmodernism so enthusiastically.
The version of Hesse's statement by the outspoken maverick G. K. Chesterton runs,
It is only the last and wildest kind of courage that can stand on a tower before ten thousand
people and tell them that twice two is four.
Leonard Cohen said, "May the lights of the Land of Plenty shine on the truth some day". They do not do so at the moment and, if we want to ensure that they do, we will need Chesterton's wild courage.