You can find your average, amateur killers on every street. They’re mostly deranged or drunk or some poor woman who’s had a hard day and the husband has raised his hand once too often and suddenly twenty years of frustration takes over. Killing a stranger without malice or satisfaction, other than the craftsman’s pride in a job well done, is such a rare talent that armies spend months trying to instil it into their young soldiers. Most people will shy away from killing people they haven’t been introduced to.

Terry Pratchett, The fifth elephant