The definitive icon of Western Christianity is the image of a crucified man in an extremity of agony.

It is an emblem of the cruelty that human beings have inflicted on one another from time immemorial. But it is also a pain that redeems the world. The Western Christian doctrine of atonement – one that is not held by the Greek Orthodox – is sometimes difficult to understand: it is hard to imagine how a compassionate God would demand such suffering as the price of our salvation.

But the French  philosopher Peter Abelard (1079-1142) suggested an alternative: when we look at the crucifix, our hearts break in  sympathy and fellow-feeling – and it is this interior move­ment of compassion and instinctive empathy that saves us.