To a greater extent than ever, those on both sides of the political fence, and even those sitting on it, are only talking and writing to and for people who already agree with them. The only time most of us engage with those who have different views from our own is when we think we have come up with a suitably sneering one-liner to launch against the tweet of someone of whom we have come to think as the enemy. One consequence of this new form of global-village parochialism is the atrophy of whatever capacity we may once have had to put ourselves in the place of this putative enemy and to see the world as he sees it—if only for the sake of better understanding and so refuting his arguments.

But why are we supposed to care about that if argument itself is now a lost art? Such appears to be the case, according to Lee Siegel’s Why Argument Matters (Yale University Press), which I have reviewed for a forthcoming number of the Claremont Review of Books. With this book, the cultural moment of the Twitterverse has found its apologist and its theorist. On Mr. Siegel’s telling, “argument” has joined that long list of words—like “lie” or “racism” or “insurrection” or “democracy” or “disinformation” or “free speech” or “fascism” or “anti-fascism”—whose meaning has now changed in common usage (common media usage, anyway) into something quite different from, or even directly opposite to,