It is a truism that a controversialist should know and understand his opponent's point of view; but where relations with non-Catholics are concerned, it may well be that the time of controversy is over and that knowledge of others is now to be regarded rather as essential material for the rebuilding of a native Catholicism than as a weapon for attack and defence. The missionary practice of the Church has always been not to destroy a people's beliefs and practices but to correct, supplement and direct them to their true end; and this applies particularly to work amongst other Christians, where we speak from faith to faith. The non-Catholic Christian already believes in and follows our Lord, although his understanding of him is incomplete; it is our task to remove from his mind those misconceptions which hinder the full realization of the truth, making it possible for him to see the Catholic faith as the complete expression of that which he now holds imperfectly.