Medieval Christian World-View of St. Thomas Aquinas M]an is directed to God, as to an end that surpasses the grasp of his reason... Whereas man's whole salvation, which is in God, depends upon the knowledge of this truth. Therefore, in order that the salvation of men might be brought about more fitly and more surely, it was necessary that they should be taught divine truths by divine revelation.

Pt. I, Q. 1, Art. 1]

For St. Thomas Aquinas, the purpose and meaning of human life in all its aspects are ultimately to be found in God and salvation: "Sacred doctrine" is thus the greatest and most important element of philosophy; for Aquinas the highest and truest philosophy is thus Christian philosophy. Sacred doctrine is not just one branch of human science among others, but the most important knowledge available to human beings, for "the purpose of this science, in so far as it is practical, it eternal bliss" [Pt. I, Q. 1, Art. 5]. Sacred doctrine deals, as its object, with something that cannot be directly apprehended or fully known by human knowledge, but only ultimately approached and understood through faith: God Himself. Yet Aquinas is clear that through sacred doctrine humanity can know enough of God and His purposes by understanding the nature of Christian salvation by "treat[ing] of God viewed as the highest cause - not only so far as He can be known through creatures just as philosophers knew Him... But also so far as He is known to Himself alone and revealed to others" [Pt. I, Q. 1, Art. 6].

The world is the creation of God and is centered, for Aquinas, on God, and all human endeavour should ultimately be directed towards a knowledge of God and the divine mystery of human salvation. It is...

Aquinas argues that human beings are made human by their intellects, and that they have the ability and duty to use their intellects to apprehend the divine. Human beings are not, thus, without standing in Aquinas's world-view, but as the objects of divine will are required to interpret and understand His will through sacred doctrine.
Sacred doctrine is ultimately based upon faith, and without faith there can be no understanding of the divine; but Aquinas argues that faith without intellectual engagement is insufficient:

This doctrine is especially based upon arguments from authority, inasmuch as its principles are obtained by revelation: thus we ought to believe on the authority of those to whom this revelation has been made... But sacred doctrine makes use even of human reason, not, indeed, to prove faith (for thereby the merit of faith would come to an end), but to make clear other things that are put forward in this doctrine. [Pt. I, Q. 1, Art. 8]

The starting points of this intellectual process are authoritative revelations of divine purpose first and most importantly through Scripture, and secondly through the interpretations of the Doctors of the Church, mediated through human faith and reason. For Aquinas faith and reason can work in harmony; there is no necessary tension between them.

God is at the heart of Aquinas's world-view and philosophy, and the role of human reason as well as faith once more comes to the fore in the process by which human beings accept the existence of God (for Aquinas is clear that the existence of God is not self-evident). The…