world is found in the New Testament, but was systematized in Saint Augustine City of God. The
dualism of the spirit and the flesh is to be found in Plato, and was emphasized by the
Neoplatonists; it is important in the teaching of Saint Paul; and it dominated the Christian
asceticism of the fourth and fifth centuries.
Catholic philosophy is divided into two periods by the dark ages, during which, in Western
Europe, intellectual activity was almost non-existent. From the conversion of Constantine to the
death of Boethius, the thoughts of Christian philosophers are still dominated by the Roman
Empire, either as an actuality or as a recent memory. The barbarians, in this period, are regarded
merely as a nuisance, not as an independent part of Christendom. There is still a civilized
community, in which all well-to-do people can read and write, and a philosopher has to appeal to
the laity as well as to the clergy. Between this period and the dark ages, at the end of the sixth
century, stands Gregory the Great, who regards himself as a subject of the Byzantine emperor, but
is lordly in his attitude to barbarian kings. After his time, throughout Western Christendom, the
separation of clergy and laity becomes more and more marked. The lay aristocracy creates the
feudal system, which slightly tempers the prevailing turbulent anarchy; Christian humility is
preached by the clergy, but practised only by the lower classes; pagan pride is embodied in the
duel, trial by battle, tournaments, and private revenge, all of which the Church dislikes but cannot
prevent. With great difficulty, beginning in the eleventh century, the Church succeeds in
emancipating itself from the feudal aristocracy, and this emancipation is one of the causes of the
emergence of Europe from the dark ages.
The first great period of Catholic philosophy was dominated by Saint Augustine, and by Plato
among the pagans. The second period culminates in Saint Thomas Aquinas, for whom, and for his
successors, Aristotle far outweighs Plato. The dualism of The City of God, however, survives in
full force. The Church represents the City of God, and politically philosophers stand for the
interests of the Church. Philosophy was concerned to defend the faith, and invoked reason to
enable it to argue with those who, like the Mohammedans, did not accept the validity of the
Christian revelation. By this invocation of reason the philosophers challenged criticism, not
merely as theologians, but as inventors of systems designed to appeal to men of no