Blaise Pascal was a man of many talents, making remarkable contributions to mathematics, physics, and even philosophy. He was also an inventor and you’d be surprised to see how many “Pascal’s Law” and “Pascal’s Constant” you’ll find in various fields of science. But the man also had a different talent: convincing others that he’s right.

Painting of Blaise Pascal made by François II Quesnel for Gérard Edelinck in 1691.

As Brain Pickings points out, Pascal proposed what’s likely the most effective way to convince someone to change their mind:

“When we wish to correct with advantage, and to show another that he errs, we must notice from what side he views the matter, for on that side it is usually true, and admit that truth to him, but reveal to him the side on which it is false. He is satisfied with that, for he sees that he was not mistaken, and that he only failed to see all sides. Now, no one is offended at not seeing everything; but one does not like to be mistaken, and that perhaps arises from the fact that man naturally cannot see everything, and that naturally he cannot err in the side he looks at, since the perceptions of our senses are always true.”

To be perfectly honest, this is arguably not manipulation — as Pascal explains how to convince a man you are right, presuming you are right. If you’re not, and your side is actually inferior, then it all falls like a sand castle. But even so, it’s quite useful to be able to get your reasoning through to someone … as we all know, that’s often quite difficult, and even sound reasoning often falls on deaf ears without the right approach.

Pascal then goes on to deliver another gem:

“People are generally better persuaded by the reasons which they have themselves discovered than by those which have come into the mind of others.”

This is simply brilliant, and it’s not just about making an argument, you can apply this to anything. A parent can tell his child not to touch the hot plate a thousand times to no avail — but if the child does get burnt a single time, he will remember it for life. You always remember the things you’ve learned yourself, and you’ll always believe in them too. Pascal suggests this can often be used in intellectual debates.

Arthur Markman, psychology professor at The University of Texas at Austin supports both these ideas. Cooperation, he says, is why the first idea works.

“One of the first things you have to do to give someone permission to change their mind is to lower their defenses and prevent them from digging their heels in to the position they already staked out,” he says. “If I immediately start to tell you all the ways in which you’re wrong, there’s no incentive for you to co-operate. But if I start by saying, ‘Ah yeah, you made a couple of really good points here, I think these are important issues,’ now you’re giving the other party a reason to want to co-operate as part of the exchange. And that gives you a chance to give voice your own concerns about their position in a way that allows co-operation.”

As for the second one, it’s also about providing an incentive for the person you’re debating, Markman says.

“If I have an idea myself, I feel I can claim ownership over that idea, as opposed to having to take your idea, which means I have to explicitly say, ‘I’m going to defer to you as the authority on this.’ Not everybody wants to do that,” he adds.

Pascal was incredibly brilliant, on a level few people in history can claim to be, and the broadness of his concerns is yet another testament to his value. Not only was he a brilliant philosopher, mathematician, and physician — he was also an applied psychologist.

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