In Why Think? Evolution and the Rational Mind, Ronald de Sousa—a long-time member of the University of Toronto Philosophy Department, now cast out into the knackers’ yard of retirement—discusses two cases of people instructed by God to kill their children. First there was the wretched Texas housewife Andrea Yates, killer of her five kids, who was found guilty of deliberate murder on the grounds that, having got her divine instructions, she planned carefully how she could drown her babies. Second, there was Abraham, no less of a planner and whose son Isaac was saved only at the last moment thanks to another message from above, not to mention a handy ram ensnared in a thicket. The one was condemned for a vile crime; the other is venerated as a founder of no fewer than three different religions. De Sousa remarks: “When enough people share a delusion, it loses its status as a psychosis and gets a religious tax exemption instead.”

At that point, I knew I was going to love this book—and it is indeed a lot of fun. Why Think? is also good and clever. I have always said that the reason why philosophers are so disliked on university campuses is that we are brighter than anyone else and have trouble concealing the fact. Ronnie de Sousa does nothing to change this perception.