A lot rides on how we structure and present our arguments. In
2013, the UK legalised same-sex marriage. John Randall, then a
Conservative MP, voted against the bill, a decision he later said he
regretted. He wished he’d talked to one of his friends in Parl iament
beforehand, someone who – to many’s surprise – had voted in favour
of marriage equality. ‘He said to me that it was something that
wouldn’t affect him at all but would give great happiness to many
people,’ Randall recalled in 2017. ‘That is an argument that I find it
difficult to find fault with.’[66]
Unfortunately, there is a major obstacle when it comes to finding a
persuasive argument. If we have a strong opinion, Bayesian
reasoning implies that we will struggle to distinguish the effects of
arguments that support this existing view. Suppose you strongly
believe in something. It could be anything from a political stance to an
opinion about a film. If someone presents you with evidence that is
consistent with your belief – regardless of whether this evidence is
compelling or weak – you will go away with a similar opinion
afterwards. Now imagine someone makes an argument against your
belief. If that argument is weak, you won’t change your view, but if it is
watertight, you might well do so. From a Bayesian point of view, we
are generally better at judging the effect of arguments that we
disagree with.[67]
That’s if we even think about different arguments. A few years ago,
social psychologists Matthew Feinberg and Robb Willer asked people
to come up with arguments that would persuade someone with an
opposing political view. They found that many people used arguments
that matched their own moral position, rather than the position of the
person they were trying to persuade. Liberals tried to appeal to
values like equality and social justice, while conservatives based their
argument on things like loyalty and respect for authority. Arguing on
familiar ground might have been a common strategy, but it wasn’t an
effective one; people were far more persuasive when they tailored
their argument to the moral values of their opponent. This suggests
that if you want to persuade a conservative, you’re better off focusing
on ideas like patriotism and community, whereas a liberal will be more
convinced by messages promoting fairness.[68]