With the subtlety of a metaphysician St. Thomas combined a vast erudition.  Quotations from the Fathers appear on nearly every page of his writings, serving either as a keynote to the discussion which follows, or as an occasion for solving objections.  Toward St. Augustine he shows the deepest reverence, though their methods differ so widely, and his brief but lucid comments throw light on difficult sayings of the great Doctor.  His familiarity with patristic theology is shown particularly in the ‘Catena Aurea,’ where he links with passages from the Sacred Text numerous extracts from the older commentators.

His respect for these interpretations did not prevent him from making a thorough search of Scripture itself.  With characteristic clearness and depth he interpreted various books of the Bible, insisting chiefly on the doctrinal meaning.  The best of his work in this line was devoted to the Pauline Epistles and to the Book of Job; but his mastery of each text is no less evident where he takes the authority of Scripture as the starting-point in theological argument, or makes it the crowning evidence at the close of a philosophical demonstration.

The materials gathered from Philosophy, Tradition, and Scripture were the fruit of analysis; the final synthesis had yet to be accomplished.  This was the scope of the ‘Summa Theologica,’ a work which, though it was not completed, is the greatest production of Thomas Aquinas.  In the prologue he says:—­

“Since the teacher of Catholic truth should instruct not only those who are advanced, but also those who are beginning, it is our purpose in this work to treat subjects pertaining to the Christian religion in a manner adapted to the instruction of beginners.  For we have considered that young students encounter various obstacles in the writings of different authors:  partly because of the multiplication of useless questions, articles, and arguments; partly because the essentials of knowledge are dealt with, not in scientific order, but according as the explanation of books required or an occasion for disputing offered; partly because the frequent repetition of the same things begets weariness and confusion in the hearer’s mind.  Endeavoring, therefore, to avoid these defects and others of a like nature, we shall try, with confidence in the Divine assistance, to treat of sacred science briefly and clearly, so far as the subject-matter will allow.”

The work intended for novices in theology, and so unpretentiously opened, is then portioned out in these words:—­

“Whereas, the chief aim of this science is to impart a knowledge of God, not only as existing in Himself, but also as the origin and end of all things, and especially of rational creatures, we therefore shall treat first of God; second, of the rational creature’s tendency toward God; third, of Christ, who as man is the way whereby we approach unto God.  Concerning God, we shall consider (1) those things which