The following Treatise is the message or teaching of S. Francis de Sales to the Calvinists of the Chablais, reluctantly written out because they would not go to hear him preach. The Saint neither published it nor named it. We have called it "The Catholic Controversy," partly to make our title correspond as nearly as possible with the title "Les Controverses," given by the French editor when the work was posthumously published, chiefly because its scope is to state and justify the Catholic doctrine as against Calvin and his fellow-heretics. It is the Catholic position, and the defence of Catholicism as such. At the same time it is incidentally the defence of Christianity, because his justification of Catholicism lies just in this that it alone is Christianity; and his argument turns entirely on the fundamental question of the exclusive authority of the Catholic Church, as the sole representative of Christianity and Christ. This is the real point at issue between the Church and the sects, and therefore he, as officer of the Church, begins by traversing the commission of those who teach against her. He shows at length, in Part I., that she alone has Mission, that she alone is sent to teach, and that thus their authority is void, and their teaching but the vain teaching of men.