3. To the department of =Dogmatics= belongs his four books Περὶ ἀρχῶν (_De Principiis_), which have come down to us in a Latin translation of Rufinus with arbitrary interpolations. His Στρωματεῖς in ten books which sought to harmonize the Christian doctrine with Greek philosophy is lost, and also his numerous writings against the heretics. His comprehensive apologetical work in eight books, _Contra Celsum_ (§ 23, 3), has come down to us complete.[76] Gregory of Nazianzus [Nazianzen] and Basil the Great made a book entirely from his writings under the title Φιλοκαλία, which contains many passages from lost treatises, and a valuable original fragment from his Περὶ ἀρχῶν. His principal doctrinal characteristics are the following: There is a twofold revelation, the primitive revelation in conscience to which the heathen owe their σπέρματα ἀληθείας, and the historical revelation in holy scripture; there are three degrees of religious knowledge, that of the ψιλὴ πίστις, an unreasoned acceptance of the truth, wrought by God immediately in the heart of men, that of γνῶσις or ἐπιστήμη to which the reasoning mind of man can reach by the speculative development of scripture revelation in his life, and finally, that of σοφία or θεωρία, the vision of God, the full enjoyment of which is attained unto only hereafter. For his doctrine of the Trinity, see § 33, 6. His cosmological, angelological and anthropological views represent a mixture of Platonic, Gnostic and spiritualistic ideas, and run out into various heterodoxies; thus, he believes in timeless or eternal creation, an ante-temporal fall of human souls, their imprisonment in earthly bodies, he denies the resurrection of the body, he believed in the animation and the need and capacity of redemption of the stars and star-spirits, in the restoration of all spirits to their original, ante-temporal blessedness and holiness, ἀποκατάστασις τῶν πάντων. 4. Of his =Ascetical Works=, the treatise Περὶ εὐχῆς with an admirable exposition of the Lord’s prayer, and a Λόγος προτρεπικὸς εἰς μαρτύριον have been preserved. Of his numerous epistles, the _Epistola ad Julium Africanum_ defends against his correspondent the genuineness of the history of Susannah. § 31.6.