The medieval Catholic Church, widely considered a source of intolerance and inquisitorial fervor, was not anti-science during the Dark Ages--in fact, the pope in the year 1000 was the leading mathematician and astronomer of his day. Called "The Scientist Pope," Gerbert of Aurillac rose from peasant beginnings to lead the church. By turns a teacher, traitor, kingmaker, and visionary, Gerbert is the first Christian known to teach math using the nine Arabic numerals and zero. In The Abacus and the Cross, Nancy Marie Brown skillfully explores the new learning Gerbert brought to Europe. A fascinating narrative of one remarkable math teacher, The Abacus and the Crosswill captivate readers of history, science, and religion alike.