Suppose you need to persuade your roommate to do the dishes. You might try to reason with them, using an argument about fairness: “I did the dishes yesterday, and it’s unfair for me to do the dishes two days in a row, so it’s your turn today.” But logical arguments don't always work, and you may find yourself resorting to guilt and shame—or even threats—to get what you want. So is logic actually that useful in persuasion? It’s great when people can be reasoned with, but unless you're living with Mr. Spock, that’s not what happens most of the time. Usually the problem isn't that someone doesn’t understand, but that they don’t want to do what you’re asking. Logic seems pretty powerless at that point.



And it's even worse when it comes to big social issues, like climate change. When you're bickering about household chores, you probably both agree at least on the premises: “taking turns is good,” "those dishes are dirty," "we must eliminate all traces of cilantro." But with climate change, some people don’t even agree it’s happening. So how can logic gain any purchase there?


Of course, you might say it’s not logic’s fault: those who deny human-made climate change have simply been fooled by propaganda, and they’re not acting logically at all. Think about that senator who brought a snowball into Congress. His argument was obviously this: “if the climate were warming, then winter wouldn’t be cold; but here’s a snowball, ergo nothing to see here.” This is sophistry, not logic. So you might say: when it comes to propaganda, logic is simply beside the point.

But in fact, logic often does come into play even when people are denying reality. For one thing, those who believe climate change isn’t real often use that belief as a premise in future arguments—so even when they do use good logic, their faulty premises will lead to false conclusions. And for another thing, the people creating the propaganda are really good at logic! They cynically use spurious premises and dodgy arguments to push dangerous conclusions.

What you often see, in propaganda, is people constructing arguments that are technically valid: that is to say, the (bad) conclusion follows logically from the (dodgy) premises. If snow in winter disproved climate change, and I’ve got a snowball in my hand, then climate change doesn’t exist. This argument isn’t a sound one—as the old saying goes, "if my aunt had wheels, she’d be a bicycle!"—but it’s a valid one. And that’s why it’s so effective at persuading unsuspecting members of the public.

Given that, what we badly need are tools for persuasion that work in the actual world. One strategy would be to appeal to emotions such as hope and fear; but another would be to make the gift of logical thinking available to all. We should teach more logic in high school, and require more of it in universities. Logic is too precious to be hoarded by a few people at a few fancy schools. If more of us were trained in logic, we’d be able to sniff out bad arguments a mile away, and no one would get away with presenting winter snowballs as a rationale for complacency.

That's not to say we don't also need empathy, art, and collective action if we’re going to tackle the big problems. But we also need logic. After all, how are you going to organize for that collective action if you can’t rationally persuade people to sign up?

 Our guest will surely have more to say about that—it's Patrick Girard from the University of Auckland, whose new book is Logic in the Wild.