When I was American editor of the Times Literary Supplement during the Clinton era, the paper published an article by the philosopher Thomas Nagel on the Monica Lewinsky affair that was much cited by Clinton’s apologists at the time. It was a plea for President Clinton to be spared the obnoxious probing of his private life that had yielded a bumper crop of headlines and that was eventually to lead to his impeachment. In the course of his article, Professor Nagel wrote that he now regretted his own support, seven years before, for a similar probing of the private life of the Supreme Court nominee Clarence Thomas by Democrats bent on denying him Senate confirmation. So apparently casual was this aside, however, that a copy editor cut it for space, and it was only the vigilance of Ferdinand Mount, the editor at the time, during a final read-through that caught the omission and restored it.

Mr. Mount saw at once that this concession, this acknowledgment of error, was essential to the article’s seriousness. Without it, Nagel’s plea would hardly have been a real argument and could have been dismissed as just another partisan rant of a kind that was common at the time and has become even more common since. Six years later it has become even easier for our public controversialists to ignore the presence of that silent interlocutor who used to whisper in our ear when we were exaggerating or contradicting ourselves or being unfair to