For Steven Pinker, as a cognitive scientist, style is ‘the effective use of words to engage the human mind’. But in the last hundred pages of his frustratingly mixed-up book, he decides on questions of usage (whether ‘data’ is a plural; the placing of apostrophes). To teach a fine style is no easy matter in a book; Pinker leans, he says, to a ‘classic style’. To discuss house style or usage is fun but bitty. You’d hardly turn to Pinker’s discussion of just a hundred ‘of the more common issues of grammar’ for guidance, but rather to a fat manual, such as Robert Burchfield’s edition of Fowler’s Modern English Usage.