Letter 822: The priesthood is a sacred trust, not a career.

To Alupios. On the Holy Trinity. The things spoken in the singular in the sacred Scriptures are characteristic of the divine nature; for the holy and royal Trinity is of one substance. But the things expressed beyond the singular number belong to the distinction of the hypostases [the three Persons]. For the Godhead is expanded into three properties, and is again contracted into one essence; so that neither may polytheism find room from the distinction of natures, nor the Jewish unity [the Jewish doctrine of a single divine Person] from the one Person. For the sameness of nature belongs to each hypostasis, while the distinctness of the hypostases is joined together into one essence. And so that we may not, by bringing everything into the open, make the letter too long, we shall take up one example or a second, and thereby cut open a road of interpretation for the rest. God would say: "I am the first, and I am after these things; before me there came to be no other God, and after me there shall be none." What then might the heterodox say? Who then is it, the Father or the Son? If, then, it is the Father, how does He say that there is none after Him? For according to you the Son is after Him. But if it is the Son who has spoken, how does He say, "Before me there came to be no other God"? For surely you would not dare to do away with the hypostasis of either one. For you have laid down as doctrine a first and also a second. But that one of the two does not exist, you would not, I think, even endure to think. For we, with respect to the consubstantial Trinity, understand both this passage and others like it; but you who divide [the Godhead], how will you interpret what has been said? Let this, then, be said concerning these matters. Let us come also to the passages that go beyond the singular number: "Let us make," He says, "man. And God made man; according to the image of God He made him." "And the Lord rained down fire and brimstone from the Lord." "And the Lord your God, the Lord is one." What then might the Jews say here? For to us nothing is contradictory, who define three hypostases as one essence; but it shuts up their mouths completely. It is clear, then, from these passages, that the crown of the Church is beyond dispute.

Περὶ τῆς ἁγίας Τριάδος. Τὰ μὲν ἑνικῶς εἰρημένα ἐν ταῖς ἱεραῖς Γραφαῖς τῆς θείας φύσεώς ἐστι χαρακτηριστικά· ὁμοουσίας γάρ ἐστιν ἡ ἁγία καὶ βασιλευτικὴ Τριάς. Τὰ δ’ ὑπὲρ τὸν ἑνικὸν ἐξενηνεγμένα ἀριθμόν, τῆς τῶν ὑποστάσεων ἐστι διαφορᾶς. Πλατύνεται γὰρ ἡ θεότης εἰς τρεῖς ἰδιότητας, καὶ συστέλλεται πάλιν εἰς μίαν οὐσίαν· ἵνα μήτε ἡ πολυθεΐα χώραν ἔχῃ ἐκ τῆς τῶν φύσεων διαφορᾶς· μήθ’ ἡ Ἰουδαϊκὴ ὁμόνοια ἐκ τοῦ ἑνὸς προσώπου. Ἡ μὲν γὰρ ταυτότης τῆς φύσεως, ὑποστάσει ἑκάστη· ἡ δὲ τῶν ὑποστάσεων ἰδιότης, εἰς μίαν οὐσίαν συνάπτεται. Καὶ ἵνα μὴ πάντ’ εἰς μέσον φέροντες μηκύνωμεν τὴν ἐπιστολήν, ἓν ἢ δεύτερον μεταχειρισάμενοι, καὶ τοῖς λοιποῖς ὁδὸν ἑρμηνείας ἀνατέμωμεν. Φαίην ὁ Θεός· «Ἐγὼ πρῶτος, καὶ ἐγὼ μετὰ ταῦτα· ἔμπροσθέν μου οὐκ ἐγένετο ἄλλος Θεός, καὶ μετ’ ἐμὲ οὐκ ἔσται.» Τί οὖν ἂν φαῖεν οἱ ἑτερόδοξοι; τίς ἄρ’ ἐστὶν ὁ Πατὴρ ἢ ὁ Υἱός; Εἰ μὲν οὖν ὁ Πατήρ, πῶς φησι μὴ εἶναι μετ’ αὐτόν; καθ’ ὑμᾶς γάρ, μετ’ αὐτόν ἐστιν ὁ Υἱός. Εἰ δὲ ὁ Υἱός ἐστιν ὁ εἰπών, πῶς φησιν, «Ἐμπροσθέν μου οὐκ ἐγένετο ἄλλος Θεός;» Οὐ γὰρ δὴ τολμήσατε θατέρου τὴν ὑπόστασιν ἀνελεῖν. Πρώτου μὲν γὰρ καὶ δεύτερον ἐδογματίσατε. Τὸ δὲ μὴ εἶναι θάτερον, οὐδ’ ἐννοῆσαι, ὡς οἶμαι, ἀνάχοισθε. Ἡμεῖς μὲν γὰρ εἰς τὴν ὁμοούσιον Τριάδα, καὶ τοῦτο καὶ τὰ τοιαῦτα ἐκλαμβάνόμεθα· ὑμεῖς δὲ οἱ διαιροῦντες πῶς ἑρμηνεύσετε τὸ εἰρημένον; Ταῦτα μὲν οὖν περὶ τούτων εἰρήσθω. Ἡῶμεν δὲ καὶ εἰς τὰ τὸν ἑνικὸν ἀριθμὸν ὑπερβαίνοντα, «Ποιήσωμεν, φησίν, ἄνθρωπον. Καὶ ἐποίησεν ὁ Θεὸς τὸν ἄνθρωπον· κατ’ εἰκόνα Θεοῦ ἐποίησεν αὐτόν.» «Καὶ ἔβρεξε Κύριος παρὰ Κυρίου πῦρ καὶ θεῖον.» «Καὶ Κύριος ὁ Θεός σου, Κύριος εἷς ἐστι.» Τί οὖν ἂν φαῖεν ἐνταῦθα Ἰουδαῖοι; Ἡμῖν μὲν γὰρ ἐναντιοῦται οὐδέν, τοῖς τρεῖς ὑποστάσεις μίαν οὐσίαν ὁριζομένοις· αὐτῶν δὲ παντελῶς ἀποκλείει τὰ στόματα. Δῆλον οὖν ἐκ τούτων ὡς ἀναμφισβήτητός ἐστιν ὁ τῆς Ἐκκλησίας στέφανος.