St. Robert Bellarmine's treatises on the main controversies in Theology between Catholics and Protestants is unparalleled in its breadth and depth of scholarship and argumentation-4 centuries later. In the third installment of the Controversies, Bellarmine takes up the Controversies on Councils, the Church Militant, and the Marks of the Church so as to present the totality of the Catholic teaching on Ecclesiology and refute the arguments of the Protestants of his day, preeminently Luther, Calvin and in addition, Greek Orthodox objections. Bellarmine's work in this area was not only standard reading, but the foundation of all subsequent treatises on Ecclesiology. For the first time, these treatises are available in English.