Do you often find yourself dancing the “reasonable tango”? This is what the sociologist Kirsty Sedgman, in On Being Unreasonable (Faber), calls the kind of polite argument that acknowledges the opponent’s point with a “Yes, but …” and carries on indefinitely, with no mutual agreement in sight. In this bracing manifesto for being just a little less civilised, she considers subjects such as what should count as bad behaviour in the theatre, what “reasonable” means in law, and why we should not “debate” with fascists. (Sunlight is not the best disinfectant, she points out; bleach is.) Does being meek ever...