It’s one of the more mysterious features of human history that people of every era and in almost every place have regularly striven to reduce their intelligence, impair their reflexes and generally ensure that everything about them functions far less well. So what is about getting drunk that we love so much? According to Mark Forsyth’s breezy new book, the best answer comes from somebody not often thought of as a classic roisterer: William James, the American philosopher and brother of Henry.