I published an essay today on the paradox of tolerance. In July a rally at Glasgow Green ended with Nazi salutes, a mile from the city's memorial to the Glaswegians who volunteered against Franco in the 1930s. That sent me back to Popper, who put the paradox in a footnote in 1945, and to the framing I find most useful: tolerance not as a virtue you owe everyone unconditionally, but as a peace treaty that only protects the people who keep it....