An Overview The thought of the Angelic Doctor, St. Thomas Aquinas (1225 - 1274 CE), was the most important and influential of the High Middle Ages. His Summa Theologiae is regarded as the most comprehensive treatment of the relation of philosophy and theology. His theories remain the foundation of the Roman Catholic Church, and study of his philosophy remains vital and important today. One important fact needs to be said at the very beginning of any study of Aquinas, that is, his attempt to integrate the various strands of medieval thought into a comprehensive system conveys a better understanding of medieval intellectual life than does any other work of any other philosopher of this period (Boylan: 14).
His natural law theory combines elements drawn from Platonic, Aristotlean, Roman Law, Stoicism, the Church Fathers, Augustine, Feudal Theory, and the practices of the various states existing in his day. In the century preceding Aquinas, the intellectual life in the West suddenly sprang to life. Philosophical speculation and argument developed rapidly. One of the more difficult elements of his treatises is the manner and record of this style of doing philosophy. Common practice among philosophers and theologians was to call a public debate over a set of theses.
Percept 1
One person would advance a positive position with respect to that thesis (the so called Avocatus Dei or God's Advocate) and the other would advance a negative position with respect to that thesis (the so called Avocatus Diaboli or Devil's Advocate) (Boylan: 16). Each would then respond to the other in a series of objections, and each would be allowed the opportunity to respond to these. This manner of presenting a thesis, hearing objections and replying to them is still practiced in Western philosophy to this day. In fact, at the final stage of philosophical development, Ph D candidates are still required to advance a set of theses and defend them orally before a committee of full professors before permission is granted to write the candidate's Dissertation.
The principle contribution of Aquinas was to develop a systematic philosophical and theological response to the challenge posed to medieval Christianity by the rediscovery of the whole of Aristotle's philosophy which, except for his works on logic, had been lost to the West until the thirteenth century. Earlier medieval thought relied for its view of the world on the Bible, Augustine, Plato and the neo-Platonists. The intellectual revival which began in the twelfth century looked to Plato as its principal philosophical inspiration, despite the fact that only his Phaedo, Meno, and part of the Timaeus were available in Latin (Paterson & Matthew : 25).
Objection 1. It would seem that in some cases it is lawful to kill the innocent. The fear of God is never manifested by sin, since on the contrary "the fear of the Lord driveth out sin" (Sirach 1:27). Now Abraham was commended in that he feared the Lord, since he was willing to slay his innocent son. Therefore one may, ...