Ten years ago I began an historical study of the figure of the Virgin Mary. I am a historian of the Middle Ages, and so I expected my work to include the study of religious imagery and prayer, hymns and Marian shrines. I also expected the most passionate interest in the figure of Mary to arise among women: working women in families or religious women in nunneries, of high status and low. I looked forward to exploring worlds of personal devotion and family worship, and these I found all over Europe and in all social contexts. What I had not expected was the extent of public and even political power possessed by this quintessential figure of motherhood. Here was a challenge: motherhood acting in the public domain.

In large parts of the world Madonnas are still to be seen on every street corner. This figure of beauty and tenderness - a young mother – gazes adoringly at her son, cradles him, or offers him her breast. Yet this pair, so intimately coupled in their own private world, has historically represented much more than the attachment between mother and son, for in medieval Europe collective enterprises – pilgrimage, crusades, conquest and mission - came to be associated with the wholesome figure of the nurturing mother. One image of Mary associated her with charitable work: feeding the hungry, visiting the sick and comforting prisoners; another saw her as a protective shield against the misfortune caused by human sin. Churches and shrines which could convincingly claim possession of a vestige of Mary’s maternal body – milk, hair, girdle, tunic – were inundated by female pilgrims, mothers-to-be in search of a safe delivery.

Perhaps that is why non-Christians were attracted to the figure of Mary too. Despite the fact that Islam and Judaism were pitted in polemic and enmity against Christianity, Mary emerged as a profoundly attractive figure. For Muslims this was – and is – an easy point of contact, since the Quran extols Mary in a chapter devoted to her, the Sura Maryam. In areas where Christians and Muslims lived side by side – in Iberia, in Syria – they sometimes visited the same Mary shrines. With Jews the relationship was much more vexed, but here too there was a fascination with the art and praise of Mary: women may have drawn healing water from wells associated with Mary, and they may have borrowed from the lyrics in her honour to praise the Talmud, as a female figure.

Irreducible and familiar motherhood – nurturing and consoling – made Mary the most accessible aspect of Christian culture, as it became a global phenomenon. In the lands of conquest and conversion – Mexico, Peru, Quebec – missionaries led with the image of a pure and loving mother. This figure suggested ways of weaving communities together, as women do, through the sharing of food, by help in the tasks of caring for the young and the old, for the sick and the poor. Motherhood is a way of being which transcends the intimacy of mother and offspring; it is a habit of radical hospitality, of generosity.

The most common images of motherhood around us these days aim at promoting consumption: commercials present mother at the dinner table, operating the washing machine, or driving the family car on the school run. Here is the contemporary mother, proficient at all tasks. Yet even these simplistic images hint at the vast back-story of care that exists beyond the household, which extends to neighbourhoods and into communities. Even in that most unusual of households - the White House - it seems right for a mother to be leading a group of neighbours in turning ornamental soil into a vegetable garden.

To cherish motherhood as a social force is not to privilege women over men, but rather to understand in a new way that charity and amity do begin at home. Motherhood’s radical impulse towards empathy and sharing is a human resource. It is rooted in the domestic but can transcend into wider spheres. Most cultures over many centuries have relegated it to the household. It is ripe to be realized as one of our least fully exploited social forces.