pursued his earlier studies, they were also
helpful in the task which he chose as his life-work. This was the
construction of a system in which all the elements of knowledge should
be harmoniously united. An undertaking so vast necessitated a long
preparation, the study of all available sources, and the elucidation of
many detailed problems. Hence, a considerable portion of St. Thomas's
works is taken up with the explanation of Peter Lombard's 'Sententiae,'
with Commentaries on Aristotle, with Expositions of Sacred Scripture,
collections from the Fathers, and various _opuscula_ or studies on
special subjects. Under the title 'Quaestiones Disputatae,' numerous
problems in philosophy and theology are discussed at length. But the
synthetic power of Aquinas is shown chiefly in the 'Contra Gentes' and
the 'Summa Theologica,' the former being a defense of Christian belief
with special reference to Arabian philosophy, and the latter a masterly
compendium of rational and revealed truth.

The conception of the 'Summa' was not altogether original. From the
earliest days of the Church, men of genius had insisted on the
reasonableness of Christian belief by showing that, though supernatural
in its origin, it did not conflict with either the facts or the laws of
human knowledge. And as these had found their highest expression in
Greek philosophy, it was natural that this philosophy should serve as a
basis for the elucidation of revealed truth. The early Fathers turned to
Plato, not only because his teaching was so spiritual, but also because
it could be so readily used as a framework for those theological
concepts which Christianity had brought into the world. Thus adopted by
men who were recognized authorities in the Church,--especially men like
Augustine and the Areopagite,--Platonism endured for centuries as the
rational element in dogmatic exposition.

Scholasticism inaugurated a new era. Patristic erudition had gathered a
wealth of theological knowledge which the Schoolmen fully appreciated.
But the same truths were to receive another setting and be treated by
different methods. Speculation changed its direction, Aristotle taking
the place of his master. The peripatetic system found able exponents in
the earlier Scholastics; but Aquinas surpassed them alike in the mastery
of the philosopher's principles and in his application of these
principles to Christian doctrine. His Commentaries on Aristotle adhere
strictly to the text,