In describing the content of Saint Thomas' philosophy one must advert, in the first place, to the Aristotelian mold in which aU his philo sophical doctrines are cast. For him Aristotle is the philosopher. On the questions of method and doctrine which divide the Platonists from the Aristotelians Saint Thomas unhesitatingly and invariably takes the side of Aristotle. In fact, he is the Christian Aristotelian in the sense in which Saint Augustine is the Christian Pla tonist. It would, however, be fatal to a proper estimation of his philosophy to overlook the elements in it which cannot be traced to Aris totle. He was no slavish imitator; he main tained as a principle of method that the argu ment from authority is (in philosophy) the weakest of all arguments. It was only in the age of decay of the philosophy of the schools, when the letter rather than the spirit ruled the tradition of Thomistic teaching, his name and the name of Aristotle were invoked as authority to put an end to all discussion.
To say that Saint Thomas was an Aristo telian means little when we remember that in his day there were mere followers of Averroes, materialists and pantheists, who might with equal justice claim to be representatives of the Stagyrite. Saint Thomas was an Aristotelian who brought to the elucidation of his Master all the tradition of Christian speculation from Justin, the first of the Apologists, down to his own immediate predecessors and contempora ries. The thought which inspired the Chris tian philosophers was that above the order of natural truth, that is, of truth which can be at tained and comprehended by the human mind unaided, there is another order of truth, the supernatural, which human reason cannot of itself attain, but which is known to us on the authority of divine revelation. Natural truth belongs to reason, and supernatural truth to faith. Christian philosophy from the beginning took its stand on the principle that these two orders of truth must, in some way, be capable of harmonious adjustment. Rationalism exag gerated the power of reason, mysticism tended to slight reason and to emphasize and unduly extend the scope of faith. Throughout the early Middle Ages these two tendencies were at war with each other in the Christian schools. It is one of Saint Thomas' chief titles to distinction that he united in his system what is true in rationalism with what is true in mysticism. The rationalism of Abelard obliterated all dis tinction between supernatural and natural truths when it treated mysteries of faith as if they were conclusions of theology and used the Scriptures as if they were sources of argument in philosophy. In an opposite sense, the mys
ticism of Erigena removed all distinction be tween the two orders of truth, when it main tained that even truths of the natural order are known to us by a special theophania, or di vine manifestation. Saint Thomas taught that the two orders of truth are distinct; that our knowledge of supernatural truth rests on the authority of revelation, while our knowledge of natural truth rests on the evidence of reason. He maintained, at the same time, that they are consonant with each other, that since God is the author of all truth there can be no con tradiction between what revelation proposes for our belief and what reason proclaims to be evident. This thought, namely, that revelation is reasonable and reason divine, crystallized the fundamental concepts of all the preceding sys tems of Christian speculation, reconciled mys ticism with rationalism and gave permanent form to the credo ut intelligam and the intelligo at credam of scholasticism. The reconciliation of reason with revelation is of interest not merely to the Christian Apologist but to the philosopher as well. For it is inspired by the desire to establish between the supernatural and the natural that relation of continuity which Greek philosophy at the highest point of its development established between the spiritual and the material.
To the controversy concerning the mode or manner of the existence of universals, which, during the 11th and 12th centuries, had been so prominently before the minds of philosophic thinkers, Saint Thomas contributed his doctrine of moderate Realism. The Nominalisti con tended that universals are mere names; the ex aggerated Realists, influenced for the most On by Plato, maintained that universals are things really existing outside the mind as completely developed universal forms. The doctrine of moderate Realism (q.v.) is that, while univer sals are not mere names but real things, they exist outside the mind not as full-blown uni versals but only as potentially universal es sences which receive their formal aspect of universality from the mind in the act by which it compares and discusses individual objects and abstracts therefrom the formally universal concept. Saint Thomas found this doctrine es tablished in the schools of his time. He adopt ed it and gave to it, as to so many other tenets of the schools, its final and most clear-cut form.