Naturally, cognitive biases work on these identities as much as any other belief, and Henri Tajfel has demonstrated that it takes very little impetus for people to form a group identity. Even arbitrary assignment to a group results in a sense of membership in the "in-group", and a natural rivalry with an "out-group". When an out-group is perceived as physically or economically threatening, they become distrusted and cognitive dissonance pushes towards discrimination or persecution. They become enemies. And hostilities on one side inevitably escalate the equivalent response on the other.
Modern secular intellectuals are quick to point the finger at religion for these failings; they are sometimes slow to recognise that other institutions are just as guilty. Even science falls prey: the labels 'heretic' and 'pseudoscience' are born of the same psychological process. When anti-religious firebrands point the finger at religions for setting up in-groups and out-groups, they frequently seem to have missed the rather obvious point that they too are defining an out-group (religion) to be their hated enemy. Paradoxically, pushing against this tendency has been a key theme in all the major religions – the ethics of Buddha, Jesus, Mohammad and others have stressed compassion and the unity of mankind. That attempts to institutionalise such ideas have only intensified the problem is perhaps the cruellest irony in the history of religion.
Part 18 of 23 in the Pentenary series.