" If the Catholic Church was naturally inclined to persecute, she would persecute in all cases alike, when there was no interest to serve but her own. Instead of adapting her conduct to circumstances, and accepting theories according to the character of the time, she would have developed a consistent theory out of her own system, and would have been most severe when she was most free from external influences, from political objects, or from temporary or national prejudices. She would have imposed acommon rule of conduct in different countries in different ages, instead of submitting to the exigencies of each time and place. Her own rule of conduct never changed. She treats it as a crime to abandon her, not to be outside her. An apostate who returns to her has a penance for his apostasy; a heretic who is converted has no penance for his heresy. Severity against those who are outside her fold is against her principles. Persecution is contrary to the nature of a universal Church; it is peculiar to the national Churches.

While the Catholic Church by her progress in freedom naturally tends to push the development of States beyond the sphere where they are still obliged to preserve the unity of religion, and whilst she extends over States in all degrees of advancement, Protestantism, which belongs to a particular age and state of society, which makes no claim to universality, and which is dependent on political connection, regards persecution, not as an accident, but as a duty.

Wherever Protestantism prevailed, intolerance became a principle of State, and was proclaimed in theory even where the Protestants were in a minority, and where the theory supplied a weapon against themselves. The Reformation made it a general law, not only against Catholics by way of self-defence or retaliation, but against all who dissented from the reformed doctrines, whom it treated, not as enemies, but as criminals,—against the Protestant sects, against Socinians, and against atheists. It was not a right, but a duty; its object was to avenge God, not to preserve order. There is no analogy between the persecution which preserves and the persecution which attacks; or between intolerance as a religious duty, and intolerance as a necessity of State. The Reformers unanimously declared persecution to be incumbent on the civil power; and the Protestant Governments universally acted upon their injunctions, until scepticism escaped the infliction of penal laws and condemned their spirit. "

― John Emerich Edward Dalberg-Acton , The History of Freedom and Other Essays