Pole replied in a long treatise afterwards published under the title /Pro ecclesiasticae unitatis Defensione/ , in which he reproved the conduct of the king, and warned him of the dangers that his religious policy might involve.

As a good example of the complete development of this advance gained by the bishops, I will mention a charter given by Charles the Fat to John, bishop of Arezzo, in the year 879, in which he confirms to him all the property and the rights of that see, and takes him under his protection, "sub immunitatis suae defensione": he then goes on to explain what this term meant, giving a full account of the extent to which a bishop's property was exempted from the jurisdiction of the judex publicus, and protected from the imposition of burdens and exactions.