Born in the castle of Roccasecca in the kingdom of Naples in Southern Italy, into the family of the counts of Aquino, Aquinas was brought up in the Benedictine monastery of Monte Cassino. At the age of fourteen he was sent to complete his studies at the university of Naples, one of the few universities of the time where a full range of Aristotelian doctrine was studied. Here he became influenced by, and at the age of twenty joined, the Dominican order. He studied in Paris, and then Cologne, under Albert the Great, and returned to Paris in 1251/2. He subsequently resided at Orvieto, Rome, Viterbo, Paris again, and Naples, constantly writing and engaging in the doctrinal and philosophical debates of the day. His works include numerous translations and commentaries on Aristotle, theological writings, and the two major texts for which he is best known, the Summa contra Gentiles (‘Against the Errors of the Infidels’), a ‘text-book’ for missionaries, and the Summa Theologiae, begun in 1266, and universally acknowledged to be the crowning achievement of medieval systematic theology.

Throughout his writings Aquinas’s major concern is to defend a ‘naturalistic’ or Aristotelian Christianity, in opposition not only to sceptics but also to the surrounding tendency to read Christianity in Neoplatonic terms, derived largely from Augustine, and also channelled to the 13th century through such writers as Avicenna. Aquinas takes issue with the occasionalism of the Neoplatonists, which reduces mankind to spectators of the world order in which all causality is ultimately an expression of God’s will; like Aristotle he is concerned to protect the notion of a genuine human agent who is the responsible author of his or her own actions. The human being is a composite, but not a queer amalgamation of two things, a soul in a body like a sailor in a ship, as Plato is supposed to have held. Like Aristotle, Aquinas held that it is meaningless to ask whether a human being is two things (soul and body) or one, just as it is meaningless to ask whether ‘the wax and the shape given to it by the stamp are one’ (De Anima, 412 b 6). On this analogy the soul is the form of the body. Life after death is possible only because a form itself does not perish (perishing is loss of form), and is therefore in some sense available to reactivate a new body. It is therefore not I who survive bodily death, but I may be resurrected if the same body becomes reanimated by the same form. It is notable that on Aquinas’s account a person has no privileged self-understanding. We understand ourselves, as we do everything else, by sense experience and abstraction, and knowing the principles of our own lives is an achievement, not a given. In the theory of knowledge Aquinas holds the Aristotelian doctrine that knowing entails some similarity between knower and known; a human’s corporeal nature therefore requires that knowledge start with sense perception. The same limitation does not apply to beings further up the chain of being, such as angels.

In the domain of theology Aquinas deploys the distinction emphasized by Eriugena between reason and faith. Although he lays out proofs of the existence of God (see Five Ways) he recognizes that there are doctrines, such as that of the Incarnation and the nature of the Trinity, known only through revelation, and whose acceptance is more a matter of moral will. God’s essence is identified with his existence, as pure actuality. God is simple, containing no potential. But we cannot obtain knowledge of what God is (his quiddity), and must remain content with descriptions that apply to him partly by way of analogy: what God reveals of himself is not himself. After a brief period in 1277 in which several of his views were condemned, the Dominicans officially imposed his teachings on that order. He was canonized in 1323, with the difficulty that his life did not display the necessary miracles being met by Pope John XXII who said that every question he answered was a miracle. His synthesis of Aristotelian philosophy and Christian doctrine was eventually to provide the main philosophical underpinnings of the Catholic church.

http://www.newadvent.org/cathen/14663b.htm A biography of Aquinas

http://www.aquinasonline.com/Bibliography/ Bibliographies of writings by or on Aquinas