Justin Martyr, The First Apology

But in no instance, not even in any of those called sons of Jupiter, did they imitate the being crucified; for it was not understood by them, all the things said of it having been put symbolically. And this, as the prophet foretold, is the greatest symbol of His power and role; as is also proved by the things which fall under our observation. For consider all the things in the world, whether without this form they could be administered or have any community. For the sea is not traversed except that trophy which is called a sail abide safe in the ship; and the earth is not ploughed without it: diggers and mechanics do not their work, except with tools which have this shape. And the human form differs from that of the irrational animals in nothing else than in its being erect and having the hands extended, and having on the face extending from the forehead what is called the nose, through which there is respiration for the living creature; and this shows no other form than that of the cross. And so it was said by the prophet, “The breath before our face is the Lord Christ.”118 From Lam. iv. 20 (Sept.). And the power of this form is shown by your own symbols on what are called “vexilla” [banners] and trophies, with which all your state possessions are made, using these as the insignia of your power and government, even though you do so unwittingly.119 [The Orientals delight in such refinements, but the “scandal of the cross” led the early Christians thus to retort upon the heathen; and the Labarum may have been the fruit of this very suggestion.] And with this form you consecrate the images of your emperors when they die, and you name them gods by inscriptions. Since, therefore, we have urged you both by reason and by an evident form, and to the utmost of our ability, we know that now we are blameless even though you disbelieve; for our part is done and finished.

[55] Ἀλλ' οὐδαμοῦ οὐδ' ἐπί τινος τῶν λεγομένων υἱῶν τοῦ Διὸς τὸ σταυρωθῆναι ἐμιμήσαντο: οὐ γὰρ ἐνοεῖτο αὐτοῖς, συμβολικῶς, ὡς προδεδήλωται, τῶν εἰς τοῦτο εἰρημένων πάντων λελεγμένων. ὅπερ, ὡς προεῖπεν ὁ προφήτης, τὸ μέγιστον σύμβολον τῆς ἰσχύος καὶ ἀρχῆς αὐτοῦ ὑπάρχει, ὡς καὶ ἐκ τῶν ὑπ' ὄψιν πιπτόντων δείκνυται: κατανοήσατε γὰρ πάντα τὰ ἐν τῷ κόσμῳ, εἰ ἄνευ τοῦ σχήματος τούτου διοικεῖται ἢ κοινωνίαν ἔχειν δύναται. θάλασσα μὲν γὰρ οὐ τέμνεται, ἢν μὴ τοῦτο τὸ τρόπαιον, ὃ καλεῖται ἱστίον, ἐν τῇ νηῒ σῶον μείνῃ: γῆ δὲ οὐκ ἀροῦται ἄνευ αὐτοῦ: σκαπανεῖς δὲ τὴν ἐργασίαν οὐ ποιοῦνται οὐδὲ βαναυσουργοὶ ὁμοίως εἰ μὴ διὰ τῶν τὸ σχῆμα τοῦτο ἐχόντων ἐργαλείων. τὸ δὲ ἀνθρώπειον σχῆμα οὐδενὶ ἄλλῳ τῶν ἀλόγων ζώων διαφέρει, ἢ τῷ ὀρθόν τε εἶναι καὶ ἔκτασιν χειρῶν ἔχειν καὶ ἐν τῷ προσώπῳ ἀπὸ τοῦ μετωπίου τεταμένον τὸν λεγόμενον μυξωτῆρα φέρειν, δι' οὗ ἥ τε ἀναπνοή ἐστι τῷ ζώῳ, καὶ οὐδὲν ἄλλο δείκνυσιν ἢ τὸ σχῆμα τοῦ σταυροῦ. καὶ διὰ τοῦ προφήτου δὲ ἐλέχθη οὕτως: Πνεῦμα πρὸ προσώπου ἡμῶν χριστὸς κύριος. καὶ τὰ παρ' ὑμῖν δὲ σύμβολα τὴν τοῦ σχήματος τούτου δύναμιν δηλοῖ, [ἵνα ἀμε]λῶμεν καὶ τῶν τροπαίων, δι' ὧν αἵ τε πρόοδοι ὑμῶν πανταχοῦ γίνονται, τῆς ἀρχῆς καὶ δυνάμεως τὰ σημεῖα ἐν τούτοις δεικνύντες, εἰ καὶ μὴ νοοῦντες τοῦτο πράττετε. καὶ τῶν παρ' ὑμῖν ἀποθνησκόντων αὐτοκρατόρων τὰς εἰκόνας ἐπὶ τούτῳ τῷ σχήματι ἀνατίθετε, καὶ θεοὺς διὰ γραμμάτων ἐπονομάζετε. καὶ διὰ λόγου οὖν καὶ σχήματος τοῦ φαινομένου, ὅση δύναμις, προτρεψάμενοι ὑμᾶς ἀνεύθυνοι οἴδαμεν λοιπὸν ὄντες, κἂν ὑμεῖς ἀπιστεῖτε: τὸ γὰρ ἡμέτερον γέγονε καὶ πεπέρανται.