With the great man who forms the subject of this Lecture are identified those principles which lay at the foundation of the Roman Catholic power for fifteen hundred years. I do not say that he is the founder of the Roman Catholic Church, for that is another question. Roman Catholicism, as a polity, or government, or institution, is one thing; and Roman Catholicism, as a religion, is quite another, although they have been often confounded. As a government, or polity, it is peculiar,--the result of the experience of ages, adapted to society and nations in a certain state of progress or development, with evils and corruptions, of course, like all other human institutions. As a religion, although it superadded many dogmas and rites which Protestants do not accept, and for which they can see no divine authority,--like auricular confession, the deification of the Virgin, indulgences for sin, and the infallibility of the Pope,--still, it has at the same time defended the cardinal principles of Christian faith and morality; such as the personality and sovereignty of God, the divinity of Christ, salvation in consequence of his sufferings and death, immortality, the final judgment, the necessity of a holy life, temperance, humility, patience, and the virtues which were taught upon the Mount and enforced by the original disciples and apostles, whose writings are accepted as inspired. In treating so important a subject as that represented by Leo the Great, we must bear in mind these distinctions. While Leo is conceded to have been a devout Christian and a noble defender of the faith as we receive it,--one of the lights of the early Christian Church, numbered even among the Fathers of the Church, with Augustine and Chrysostom,--his special claim to greatness is that to him we trace some of the first great developments of the Roman Catholic power as an institution. More than any other one man, he laid the foundation-stone of that edifice which alike sheltered and imprisoned the European nations for more than a thousand years. He was not a great theologian like Augustine, or preacher like Chrysostom, but he was a great bishop like Ambrose,--even far greater, inasmuch as he was the organizer of new forces in the administration of his important diocese. In fact he was a great statesman, as the more able of the popes always aspired to be. He was the associate and equal of princes.