So you think compassion means being nice to people? Sure, its Latin root literally means ‘to suffer with another’, which is pretty close to the psychological concept of ‘affective empathy’, where you share in or mirror someone else’s emotional state. When I feel your pain or suffering, I may well do something to help you out.

But there’s much more to compassion than that. It’s time we recognised it as a source of radical social change which can erode prejudice, create human bonds across social divides, and spur political action. A flowering of compassion was at the roots of the anti-slavery movement in the eighteenth century, the creation of organisations to tackle child poverty in the nineteenth, and countless other political initiatives. ‘So often when people hear about suffering in our world they feel guilty,’ says Desmond Tutu, ‘but rarely does guilt actually motivate action like empathy or compassion.’

What are the origins of this more politically charged approach to compassion? I trace it back to the year 1206, when Giovanni Bernadone, the twenty-three-year-old son of a wealthy merchant, went on a pilgrimage to the Basilica of St Peter’s in Rome. He could not help noticing the contrast between the opulence and lavishness within the basilica – the brilliant mosaics, the spiral columns – and the poverty of the beggars sitting outside its doors. He persuaded one of them to exchange clothes with him and spent the rest of the day in rags begging for alms.

Not long after, when Giovanni was out riding near his home town, he met a leper. Lepers were the outcasts of medieval society, and were both shunned and despised. Many were deformed and crippled, with missing noses and bleeding sores. They were forbidden to enter towns and to drink from wells or springs. Nobody would touch them for fear of contracting their dreaded disease. But Giovanni forced himself to stifle his immediate feeling of revulsion for lepers, which he had harboured since childhood. He dismounted his horse, gave the leper a coin and kissed his hand. The leper kissed him in return.

These episodes were turning points in the young man’s life. He soon founded a religious order whose brothers worked for the poor and in the leper houses, and who gave up their worldly goods to live in poverty, like those whom they served. Giovanni Bernadone, known to us now as St Francis of Assisi, is remembered for declaring, ‘Give me the treasure of sublime poverty: permit the distinctive sign of our order to be that it does not possess anything of its own beneath the sun, for the glory of your name, and that it have no other patrimony than begging.’

St Francis’s life was an instance of radical compassion in action, one which has been an inspiration to social and political activists for over 800 years. If we want to take compassion seriously, we should think about how we might follow his example by stepping into the shoes of those whose lives might be very different from our own. Clothes swap anyone?

You can watch the famous moment when St Francis meets the leper in Roberto Rossellini’s superb film The Flowers of St Francis (1950) here.

I’ll be introducing religious historian Karen Armstrong’s sermon at The School of Life on November 20, where she’ll be talking about her book Twelve Steps to a Compassionate Life.