What is the theme in The Memory Palace of Matteo Ricci by Jonathan D. Spence?

Missionary work is another theme. In 1534, Ignatius of Loyola and six friends of his from the University of Paris formed the Society of Jesus, or the Jesuit Order. They made vows of poverty and chastity to bind themselves together and promised to do hospital and missionary work in Jerusalem, and to always and immediately obey the Pope in whatever he asked. In 1540, after some political conflicts, the order was officially accepted into the Catholic Church. The Jesuits began to expand rapidly, achieving great fame and power due to their great knowledge, powerful charity, political strategizing and zeal for their religion. Within fifty years of the founding of the Jesuit order, Matteo Ricci became a member.