The Italian mystic St. Catherine of Siena (1347-1380) was a woman of intense prayer and close union with God. She was also active in political affairs and influenced the return of the papacy from Avignon to Rome.

The twenty-third child of the Benincasa family, Catherine was born in Siena. She was a cheerful, bright, and intensely religious child, who later said she had vowed her virginity to Christ at the age of 7 when she had her first vision of Him. At 13 she joined the Dominican Sisters of Penitence in Siena. By the time she was 20, Catherine had become so widely known for her personal holiness and asceticism that she attracted a group of spiritual disciples--priests and laymen, men and women.

The many letters she dictated during the next 10 years show that her interest broadened from the religious to the political affairs of the time. The city-state of Florence...