In his book “Summa Contra Gentiles,” Thomas Aquinas made the connection between faith and reason, and heavily cites Aristotle as his logical influence. Aquinas did not put forth arguments like “the universe couldn’t have been started unless there was a God.” Instead, he referenced the Aristotelian idea that no potential can actualize itself unless it is created by something. Aquinas used an analogy for God the Father working through Jesus Christ, such as if you hit something with a stick, the stick is being struck against the object, but the stick couldn’t have done it without your hand. 

Thomas Aquinas confirmed two vital things: God exists, and He is pure. Because of these truths, Aquinas derived the following divine attributes: first, monotheism follows from God as a pure act; second, God is immaterial, since He cannot be changed; third, He is all-powerful, and causes everything that happens on earth; fourth, humans have intellect and will, and were made in the image of God, so He must also have those qualities; fifth, God is a good God, and has no negative features. 

Aquinas followed in the footsteps of Augustine of Hippo, who he claimed was one of the most significant early Christian scholars. Although he believed that war is inherently evil and can only be justified by the aggressor, Aquinas stated that there are some circumstances under which a war should be waged. 

Fransico de Victoria (1483-1546) proclaimed that princes should seek to live in peace, However if there is a war, it should be waged within just limits and followed by a period of moderation if possible. 

The Church eventually put restrictions on war, such as prohibiting crimes like robbing churches or peasants, leaving women and children alone, and not burning civilian homes. Christians also agreed to stop fighting on feast days.

John Duns Scotus (1265-1308) was an Scottish franciscan who taught theology at Oxford University. Scotus asserted that the existence of God, the immorality of the soul, and the providence of God are all truths, although none are  knowable by reason. However, it is by faith that one believes, he said. Scotus emphasised on the divine will and stated that whatever God wills is always good. 

William of Ockham, a colleague of Scotus, claimed that things do not have essences or natures and that reason and faith are separate. He stressed God’s will, stating that God could save the guilty and damn the righteous if He willed it. Interestingly, both of these scholars opposed Thomas Aquinas, who thought that reason and faith worked together in unison. 

During the 12th Century, there was a revival of Classic Latin works from the time of the Romans, which was known as the 12th Century Renaissance. John of Salisbury (d. 1180) was one of the most knowledgeable finders of Roman poetry during this period and helped bring about a resurgence of poets like Virgil, Ovid, and Cicero. This era also focused on philosophy and science, with many Muslim astronomers and doctors translating old Greek works in Arabic. Due to this renaissance in thinking, European universities started requiring students to read all of Aristotle’s works. 

The universities of the Middle Ages were the first scholarly systems which had a fixed program of study. Degrees were first invented, and taught students to hone their expertise in a certain subject. Some major early universities include Oxford, Cambridge, Paris, and Bologna. During this time, universities needed a charter from either the Pope or the Holy Roman Emperor to start, and the Church often assisted in funding the university in return. 

Scholastic Philosophy was a movement from Positive Theology to Speculative Theology, which is the study of faith that is consistent with reason. St. Anselm (1033-1109) and Peter Abelard (1079-1142) were pivotal renaissance writers who asked questions about the proof of God’s existence. Peter Lombard (1096-1160) wrote four books covering God, the Trinity, and the Creation of Man. St. Albert the Great (1200-1280), known as one of the greatest scholars and theologians of the Middle Ages, also studied Scholastic Philosophy during the period. 

Thomas Aquinas (1225-1274) was one of the most influential theologians of the late Middle Ages. He attended the University of Naples as a young man and entered the Dominicans  at the age of 19. His family was opposed to this and imprisoned him for a year, during which he memorized the Bible and decided to become a theologian. Aquinas studied in Paris and eventually taught theology in universities in Paris, Cologne, Bologna, Rome, and Naples, even assisting the Pope with his theological studies and writing hymns. Rivaling the writings of Aristotle, Aquinas tried to connect Christian theology to old Greek philosophy. 

Because he wanted to focus on intellectual work, Thomas Aquinas refused Pope Clement IV’s offer to become the Archbishop of Naples. He wrote that there were three kinds of knowledge: knowledge from reason alone, knowledge from reason and revelation, and knowledge from revelation alone. Thomas Aquinas inspired the western Catholic Christians to become more interested in philosophy and reason as opposed to the Eastern Orthodox, who continued to focus on the traditional faith that had been practiced since the time of Christ: one that was more mystical in nature, and less man-centered.