To the period extending from the beginning of the Christian era to the
end of the third century belong the great Apologists, such as Justin
Martyr (100-160), Athenagoras (died about 180),
Tatian, and Theophilus (both belong to the end of the
second century), who devoted their attention to the defense of
Christianity against the last attacks of the representatives of pagan
civilization. The period includes also Irenaeus (140-202),
Hippolytus (first half of the third century), and
Tertullian (160-240), whose life work consisted in the
refutation of the Gnostics and other heretics. Finally the period
includes Clement of Alexandria, Origen, Arnobius, and
Lactantius, who, during the third and fourth centuries,
expounded in their catechetical treatises the dogmas of Christianity,
and developed in their exposition the first systems of constructive
Tertullian's hostile attitude towards philosophy is expressed in the
well-known Credo quia absurdum, which is attributed to him.
It must be remembered, however, that Tertullian, being a
controversialist, was not always so measured in his language as he
might have been, had he, like Clement and Origen, devoted himself to
the task of building up a system of positive doctrine.
Clement of Alexandria  (died about A.D. 217), in the
Cohortatio ad Gentes, the Pedagogus, and the
Stromata (Strômateis), exposes the extravagances
and absurdities of paganism, and undertakes a systematic arrangement
and defense of the moral and dogmatic teachings of the Church.
Following Justin, he maintains on the one hand that whatever is true
in Greek philosophy is to be traced to the Divine Logos, who
"enlighteneth every man that cometh into the world," and on the other
hand that whatever errors are found in Greek philosophy must be
attributed to man's weak and erring nature. The true gnosis is not the
alleged esoteric doctrine of Christ, but the teaching of the Gospels
and of the Church which Christ founded. He who assents to the teaching
of Christ and the Church, without striving, by the aid of philosophy,
to give an intellectual basis to his assent, possesses faith, but he
does not possess the gnosis, which is to faith what the full-grown man
is to the child. Just as the Stoics idealized the "wise man," so did
Clement set up the Christian Gnostic as the idealized type of the
 Cf. Fessler-Jungmann, op. cit., Vol. I, pp. 277 ff.
Origen  (185-254), a disciple of Clement, possessed by far the
most synthetic mind among the Christian writers of this period. In his
work, peri archôn, he exhibits a sense of system more
imperative than that shown by any of his predecessors or
contemporaries. He assimilated into his exposition of Christian dogma,
elements from Plato, Aristotle, Philo, the Neo-Platonists, and the
Gnostics. On such questions as the preexistence of the human soul, the
eternity of the world, and the final return of all things to God
(apokatastasis), his orthodoxy has been a matter of dispute. His
greatest achievement was the scientific
formulation of the creationist account of the origin of the universe.
It is true that Clement also taught the doctrine of creation, but he
did not develop it so systematically as did Origen.
 Ibid., pp. 282 ff.
Historical Position. Clement and Origen are representatives of
the great school of Alexandrian speculation which, in the third
century, renewed the intellectual and philosophical prestige of the
ancient capital of Egypt. Successful as Greek philosophy had been in
defining the relations between matter and spirit, it had failed to
determine satisfactorily the notion of personality and to explain the
origin of primal matter. This is what Patristic speculation
accomplished by its definition of the personalities of the Divine
Trinity and by its doctrine of creation. The work begun by Clement and
Origen was completed by their successors after the Council of Nicaea.