A very different role was forced on Mary by some medieval Christians: ballast against the Jews. Chronicles, plays and prayers tell of Mary turning her back on her people and condemning the Jews as Jesus's murderers. For their own part, some Jews defended themselves against crusading Christianity by vilifying Christ's mother as, in the words of the 11th-century Rabbi Kalonicos, "a menstruating and wanton woman".

Rubin, a medieval historian, draws on folk legend, art, history and literature to convey Mary as a multi-layered persona who - from the medieval peasant to the 20th-century communist painter Käthe Kollwitz - has captured the imagination. Relying on impressive scholarship, Rubin shows how Mary, meek and mild, maternal and infinitely compassionate, shaped culture and even history more than any dictator. In her name, women lived independently of men and families; and the oppressed over-threw dictatorships. In her name, too, Jews were persecuted, Crusaders battled, Inquisitors probed. Anyone who questions the power of religious faith will find in "Mother of God" an eloquent warning.