At a recent ASR pub night one of our speakers was told that he had used an ad hominem to describe some of the targets of his talk, and I immediately noticed that the accuser was incorrect. Our speaker was an erudite man, so rather than butt in I allowed him to handle the complaint. He explained his opinions quite well – but not why what he’d said was not an ad hominem. So let’s attempt to clear the air, because the reasoning is easily understood.