It is said that during Plato’s long life no one ever saw him smile. I can readily believe it. As preparation for chairing an event at the Edinburgh Book Festival I have been reacquainting myself with Plato’s Republic, the cornerstone of western philosophy and a sober work. I first read it during my student days at St Andrews University, where the study of philosophy was compulsory at the time. Our first lecture on Republic was delivered by the professor of ancient philosophy, an intimidating and rather revered figure, who kicked off by stating Plato’s belief that men in their natural states were ignorant benighted beasts in need of rigorous control. After a practised pause, he peered over his spectacles, surveyed his audience and announced in imperious tones: “On the current evidence before me Plato was right.” Alas, much of the philosophy faded over the years, yet this cheap insult made it through the hippocampus to reside in my long-term memory.