In other words, we have to find alternative activities to give us that sense of feeling alive, of belonging and purpose. James’s argument is that human beings need to find activities that provide the same positive effects of warfare but which don’t involve the same devastation, or as he calls it, “the moral equivalent of war”. These young men see themselves as fighting a just cause with fellow Muslims, but they’re surely also seeking the sense of being more alive that James describes: a sense of cohesion and honour, which they – perhaps romantically – feel is more attainable in war than at home in the UK.

It’s easy to see how James’s ideas could apply to the large numbers of young British men volunteering to fight in Syria in recent months. This seems tantamount to suggesting that human beings fight wars because we enjoy doing so. Warfare also enables the expression of higher human qualities that often lie dormant in ordinary life, such as courage and self-sacrifice. It supplies meaning and purpose, transcending the monotony of everyday life. It brings a sense of cohesion, with communal goals, and inspires individual citizens (not just soldiers) to behave honourably and unselfishly, in the service of a greater good. It binds people together – not just the army engaged in battle, but the whole community. It creates a sense of unity in the face of a collective threat. The early American psychologist William James once suggested that war is so prevalent because of its positive psychological effects. Writing of the German people’s response to the war, the historian Alan Bullock described “an unparalleled sense of national unity, which those who experienced it never forgot, an exalted sense of patriotism”. This celebratory mood was widespread throughout Europe. When Great Britain joined the first world war, in August 1914, massive crowds celebrated outside Buckingham Palace.

Box fight and zone wars