There are mystics who seem very remote from our turbulent times, those who retire into the desert or behind the walls of convents to live their lives of contemplation apart from the world and its cares. And there are others who carry their lives of union with God straight into the world, like a leaven spreading through the lump of indifference and sin. Of these is St Catherine of Siena, the dyer’s daughter, who made her way from the plain little room in her parents’ house to the palace of the popes in Avignon, who braved revolutionary crowds and wrote letters to cardinals and kings, and all through her life preserved her uninterrupted union with God in times perhaps as unsettled as our own. What was it that made such a life possible; what were the doctrines on which it was built? She herself has given us the answer in her Dialogue and Letters, which contain a wealth of mystical thought from which a few gleanings may serve to show whence she derived that extraordinary force that made her one of the most powerful women in history.