HLA Hart revived the philosophical study of law in England. Since his concern was with a particular set of philosophical issues, it is unfair to criticise him (as some do) for not addressing different questions, such as how judges have or should work. The jurist should rather explore the flaws at the centre of Hart's project, and this is what Brian Simpson does in his final book, Reflections on 'The Concept of Law' (2011). Hart aimed to provide a definition or description of law which any person working within the practice would recognise. But if we try to get into the minds of lawyers from different times and places, we will find that Hart's 'concept' would not describe a world they would recognise.