John of Salisbury
John of Salisbury (born c. 1120; died c. 1180) built upon a logical extension of the work of St. Augustine when it is applied explicitly to the relationship between politics and religion. While St. Augustine’s work was more of an abstract defense of Christianity and an imagining of what an ideal society would look like, John of Salisbury argued directly for the supremacy of ecclesiastical power over temporal powers.
In The Statesman's Book, John of Salisbury argued for the divine right of kings:
In this manner, John of Salisbury argued that what is just is defined by the will of the Prince, because not only is the Prince’s authority derived from God, but he is subject only to God, and is God’s representative on Earth. Despite this, John of Salisbury does put forth one independent measure with which a ruler can be judged. He says that a tyrant is a ruler that forces his subjects away from God, whereas a Prince is one that brings his subjects closer to God.