Thread by @nathankw

After I retweeted this statement calling for mutual tolerance of differing views, many replied asking if I'd heard of Karl Popper's Paradox of Tolerance. I'm lucky enough to have studied Philosophy of Science at Cambridge so yes, I do know it and have read lots of Popper. 1/x

In contrast (& I hope I'm not being mean), I suspect many of those who asked had only heard of Popper from a cartoon graphic that's popular on social media. It's therefore not surprising that they are grossly distorting Popper's argument. I hope they'll find this 🧵 useful 2/x

The key to Popper's philosophy is the fallibility of human thought. However convinced we are that something is true (in science or politics), we should always recognise that it may be false. "What if I am wrong and you are right?" we should constantly ask ourselves. 3/x

Popper's answer to this problem is that, however certain you are, you should always subject your ideas to constant challenge: by experiment (in science) and through rational debate (in politics). This means that freedom of thought and speech is absolutely central to Popper. 4/x

But Popper, drawing on Plato, recognises a paradox. If one side refuses to allow debate, suppresses any contrary view and answers any verbal challenge with violence - they may succeed in stopping all debate. This is then fatal as ideas can no longer be challenged. 5/x

This is true even if (indeed particularly if), the side suppressing free speech believes it is on the moral side. So any side that is intolerant of dissent, that refuses to engage in that vital debate, should itself be treated with intolerance. This is the paradox 6/x

It's not about being intolerant towards views you see as utterly reprehensible, or even views that you believe would harm people. It's intolerance against those who would prevent any rational debate. Remember, "what if you are wrong and they are right?" 7/x

So does this apply to the current debate around sex and gender. Perhaps. The question is not who is right - either side could be wrong. The question is does one side try to suppress discussion and open debate - such as Stonewall's #nodebate policy? 8/x

Does one side threaten violence against those they disagree with? "Answer arguments by use of their fists" as Popper put it? If so, that is the side we shouldn't tolerate. If you think Popper has something useful to say (and I think he does) then your duty is to challenge ... 9/x

anyone (but particularly your own side) who tries to suppress the rational discussion of ideas. Because remember, however certain you are that you are on the right side, you may be wrong. And the only way you'll know is through rational debate with those you disagree with 10/10