Liz Truss was spot-on in arguing that the only way in which a state can flourish is by combining low taxes with economic growth. But she failed to persuade her audience that she knew how this could be achieved. If only Dr Kwarteng, a classicist, had drawn her attention to Aristotle’s Art of Rhetoric (4th century bc), the first full analysis of the means of persuasion, the day and her career would have been saved.