Unthinkable: How do we ‘know’ anything?

Relativist thinkers are providing a ‘smokescreen’ for the likes of Donald Trump, warns professor of logic Timothy Williamson

What does it mean to say we are in a “post-truth world”? A bunch of liars are in charge. Yes that but also a decline in the appreciation of reason.

A relativistic streak – always present in public debate – has overwhelmed traditional methods of distinguishing fact from fiction.

This slide has been a long time coming, and can be traced right back to the Enlightenment when the discrediting of objective truth began. The advance of relativism – the notion that truth is relative to each individual's standpoint – reached what might be seen as a new low with the recent claim by Donald Trump's senior adviser Kellyanne Conway that there are such things as "alternative facts". (She went so far as to cite a non-existent "Bowling Green massacre" to justify Trump's refugee travel ban, something she later described as a "misspeak".)

However, Trump or no Trump, there is an urgent need for some kind of public education programme surrounding truth. Few people leaving school or college have been formally instructed in logic, and there is shockingly little public understanding of how knowledge is created.


Prof Timothy Williamson, Wykeham Professor of Logic at the University of Oxford, has responded to the challenge by writing an entertaining and perspective-altering introduction to the philosophy of disagreement. Tetralogue - I'm Right, You're Wrong imagines a dialogue between four people with radically different outlooks on the world and how their conflict might be resolved, or at least mediated.

In the “Unthinkable” chair this week, Williamson has a message not just for narrow-minded conservatives but also those atheistic liberals who believe the only possible knowledge is scientific in nature.

“Knowledge doesn’t require infallibility,” he says. “What it requires is that, in the situation, you couldn’t too easily have been mistaken.”

It’s often said in debates “you’re entitled to your own opinion” but are you really so entitled?

Tim Williamson: “A totalitarian state where it’s illegal to have unorthodox opinions is a nightmare. But think of a Holocaust-denier who just shrugs his shoulders and says ‘I’m entitled to my opinion’ when presented with overwhelming evidence that the Holocaust really happened.

“What he’s doing is not okay. In both a rational and an ethical sense, he’s not entitled to ignore the evidence on something so important.

“Not to be coy about my political opinions, the Brexit vote and the Trump election resulted from many people voting on the basis of bigoted, ill-informed opinions they felt entitled to. Brexit is likely to have bad consequences in these islands, Trump in the whole world.

“It’s in the nature of opinions that people act on them, in ways that affect others as well as themselves, so it can’t be morally indifferent what opinions they hold. But not all moral matters are suitable for legislation.”

A critical point in ‘Tetralogue’ sees one of the characters quoting Aristotle: “To say of what is that it is not, or of what is not that it is, is false, while to say of what is that it is, or of what is not that it is not, is true.” Do you regard this manoeuvre as key to a more logical public debate?

“No philosophical manoeuvre can stop politicians telling lies. But some philosophical manoeuvres do help politicians obscure the distinction between truth and falsity.

"When I visited Lima, a woman interviewed me for YouTube. She had recently interviewed a 'postmodernist' philosopher. When she pointed at a black chair and asked 'Is that chair black or white?' he replied 'Things are not so simple'.

“The more philosophers take up such obscurantist lines, the more spurious intellectual respectability they give to those who try to confuse the issues in public debate when they are caught out in lies. Of course, many things in public affairs are genuinely very complicated, but that’s all the more reason not to bring in bogus complexity.

“Aristotle’s view of truth and falsity is simple, and I think fundamentally correct. Since there was no Bowling Green massacre, anyone who says there was a Bowling Green massacre is speaking falsely, and anyone who says there wasn’t is speaking truly, end of story.

“Obviously it wasn’t mainly postmodernism or relativism that won it for Trump, indeed those philosophical views are presumably more widespread amongst his liberal opponents than amongst his supporters, perhaps most of whom have never heard of them. Still, those who think it somehow intolerant to classify beliefs as true or false should be aware that they are making it easier for people like Trump, by providing them with a kind of smokescreen.”

Whatever about the "alternative facts", how would you respond to the claim that knowledge always contains some human bias, giving rise to alternative bodies of knowledge?

“Of course, all human knowledge reflects the limitations of those who get it. You know things that I don’t know and I know things that you don’t know. But our bodies of knowledge are only alternatives in the harmless sense that they are different from each other. They don’t conflict.

“What can’t happen is that two bodies of knowledge are inconsistent with each other.

“For example, if you know that there was no Bowling Green massacre, then Kellyanne Conway doesn’t know that there was one - though she may wrongly think that she knows. The reason is a simple logical principle: whatever is known is the case.

“If anyone knows there was a Bowling Green massacre then there was such a massacre, and if anyone knows there was no Bowling Green massacre then there was none.

“Although we all have biases, they don’t influence all our thoughts equally. We can still know plenty of stuff. On matters where we are too much under the influence, we just have opinions, not knowledge.”

Does knowledge require proof?

“You can know that you are feeling an itch without being able to prove it to anyone else. You can know that you sneezed ten minutes ago without being able to prove it even to yourself. The ability to justify one’s beliefs in words has more to do with the gift of the gab than with whether one really knows.

“I’m an atheist, so I don’t think anyone knows there is a god. But the mere fact that theists can’t prove to anyone that there is a god is not enough to show that they don’t know.

“If there were a god, he or she might be able to reveal himself or herself to people, and let them know of his or her existence, in ways that would not enable them to provide independent proof. But it would not be an easy trick to pull off, since it would have to be done in ways not undermined by many people’s strong antecedent desire to believe that there is a god.”

How does moral knowledge differ from scientific knowledge? How do we know anything morally?

“Most ordinary knowledge isn’t like scientific knowledge – it’s much less systematic, much less informed by abstract theory, not based on experiment or measurement. Moral knowledge is like other ordinary knowledge in those ways.

“Suppose you witness a boy teasing a girl about her skin colour. You know that he’s teasing her, and you know that he’s wronging her. Each bit of knowledge require an ability to recognise an abstract pattern in your experience – the teasing pattern and the wronging pattern. Those are much subtler patterns to recognise than triangles or circles, but you can do it.

“Why is it knowledge, not just opinion? Knowledge doesn’t require infallibility; what it requires is that, in the situation, you couldn’t too easily have been mistaken.

“If you are psychologically sensitive, you couldn’t too easily have been mistaken about the teasing. If you are morally sensitive, you couldn’t too easily have been mistaken about the wronging.”


Ask a sage:


Question: Should the study of logic be compulsory for all adults?

C.S. Peirce answers: "Few persons care to study logic, because everybody perceives himself to be highly proficient enough in the art of reasoning already."