McDonald traces the historical shift in the nature of 'barbarians'. In early civilisations, the threat of barbarians came from outside society. In the late 20th and early 21st centuries the threat may come from within. Whatever the source of the threat 'The barbarians are still our all-purpose solution to imponderable social ills, they still allow civilised beings to indulge in occasional uncivilised acts. As long as we have them in reserve, we need never get too close to our problems.'