There are two sorts of carelessness that a reviewer of history books will regularly see. The first is a minor marring of virtue: a small blot on a show of swashbuckling confidence and command over grand themes, a lack of care for what lesser men may think, arrogance even. We often call this being carefree rather than careless. The critic can correct and admire and move on. The second sort of carelessness is unsettling, almost a vice: a show of unconcern and shallow understanding, an arrogance of a different kind, a lack of care of any kind. In his lengthy account of the history of Rome, Robert Hughes is doubly, gloriously, and disgracefully careless.