To varying degrees, Jewish and Christian theologians have traditionally affirmed the doctrine that God is ineffable, which is to say, that God is beyond our rational comprehension to some extent. Maimonides begins his definition of divine ineffability by saying, "We are only able to apprehend the fact that He is and cannot apprehend his quiddity." (Guide to the Perplexed, 1190b) One practical definition of ineffability is to say that some entity a is ineffable iff it is impossible for any intellect to comprehend what sort of thing it is or to define it. Here, I talk about the doctrine and how it develops in the eastern patristic tradition somewhat.
1. Biblical Opinions
In the book of Exodus (33:20), God says to the prophet Moses “you cannot see my face; for man shall not see me and live. These words are taken in the plain sense by the author of the J source, God has a corporeal form and Moses is permitted to see the back of God but not his face. God tells Moses that he shall stand upon a rock, “and I will cover you with my hand until I have passed by; then I will take away my hand, and you shall see my back but my face shall not be seen.” (Exodus 33:21-23) These words are fulfilled literally in the story that follows, Moses stands upon the rock and God descends from heaven—his back is seen but his face is not. (Exodus 33:20–34:35) Elsewhere in the J material, God is as an embodied being who occasionally descends to earth, even eating meals on occasion, and who dwelled in the tabernacle with Israel in the wilderness. (Genesis 3:8; 11:5; 18:8; Exodus 17:1; 25:9-11) But this vision of God as an embodied being who occasionally descends to earth especially when evoked by Moses) is not shared by all of the Pentateuchal authors.
“As noted, in J, Yahweh accompanies the Israelites, in the form of the pillar of cloud (by day) and fire (by night) introduced already in Exodus 13:21–22 and mentioned again in Exodus 14:19–20, 24 and Numbers 14:14. In P, the divine presence dwells in the Tabernacle at all times, as indicated by the cloud that sits in the Tent of Meeting. In E, however, the cloud that signifies the presence of the deity is not constantly present as in J and P; it appears only when Moses goes into the Tent of Meeting to communicate with Yahweh (Exod 33:9–10). It is thus a distinctive feature of E’s historical presentation that Yahweh is not present among the people but appears only when called upon by Moses.” [Joel S. Baden, The Composition of the Pentateuch: Renewing the Documentary Hypothesis. Yale University Press, New Haven & London, 2012, p. 98.]
The views of the New Testament authors are more sophisticated, rather than an embodied God whose face is too glorious to be seen, the Johannine works teach that “God is a spirit.” (Joh. 4:24) Because God is a spirit, the Evangelist presents Jesus of Nazareth as saying it matters not whether men worship him at Mount Sinai or Mount Gerizim, or any other place. (Joh. 4:19-24; cf. De Principiis, 1.1.4.) In other words, God is not physical, so any place is as good as another to worship him. A radical departure from the Old Testament passages which claim that he must be worshiped in Zion, because “this is my resting place forever; here I will dwell, for I have desired it.” (Psa. 132:13-14; Deut. 12:5-6; 1 Sam. 8:29-30; 2 Chron. 7:12, 16) [The Samaritan Pentateuch replaces Zion and Sinai with Gerizim in the relevant places.] While the Pentateuch says only that the face of God may not be seen, there are more absolute statements in the New Testament, where it is denied that God has been seen at all. The gospel of John (1:18) says “No one has seen God at any time; the only begotten God who is in the bosom of the Father, He has explained Him,” And again, “Not that anyone has seen the Father except he who is from God; he has seen the Father." (Joh. 6:46) The first epistle of John (4:12) likewise, “No one has ever seen God.” But in the same epistle it is claimed, “we know that when he appears we shall be like him, for we shall see him as he is.” (1 Joh. 3:2) Likewise, the third epistle of John (1:11) claims that “the one who does evil has not seen God.” Hence, even within the same epistle God is depicted as unseen and yet one who will be seen by the blessed in heaven. The pastoral epistles not only say that he is “invisible” but that “no one has ever seen or can see him.” (1 Tim. 1:17; 6:16) Paul gives him the title “the invisible God.” (Col. 1:15; cf. Rom. 1:20; Heb. 11:27) But in the gospel of Matthew (18:10) we find the saying “angels always behold the face of my Father who is in heaven.” From these passages there is depicted a God who is both seen and unseen, familiar and yet distant.
2. The Eastern Fathers
The Eastern Fathers sought to explain how it is true that “no one has ever seen God” and yet that the saints “shall see him as he is” in the blessedness of the beatific vision. (1 Joh. 3:2; 4:12) They claimed that the divine essence is utterly ineffable, incomprehensible and unknowable by any created intellect. The founder of the Alexandrian school, Origen, taught that it is absurd to “think of God as in any degree corporeal [or embodied], we go on to say that, according to strict truth, God is incomprehensible and incapable of being measured.” (De Principiis 1.1.5.) Dionysius the Areopagite tells us, “He cannot be known by the senses, nor in an image, nor by opinion, nor by reason, nor by knowledge.” (De divinis nominibus 1.5) As in John of Damascus, “As regards what God is, it is impossible to say what he is in his essence, so it is better to discuss him by abstraction from all things.” (Expos. Fidei 1.4) The divine essence is transcendent and must be discussed by “abstraction” as John explains, which is to say, negatively. When Scripture says “God is light,” (1 Joh. 1:5) the meaning is explained this way, “He is not light but above light: and when we speak of Him as light, we mean that He is not darkness.” (Expos. Fidei 1.4) Elsewhere, using semi-paradoxical language he describes the divine essence as super-essential or beyond existence, ὑπεροὐσία, “because he transcends all existing things, even existence itself.” (Ibid.) As Dionysius also says, “He is neither conceived, nor expressed, nor named. And He is not any of existing things, nor is He known in any one of existing things. And He is all in all, and nothing in none. And He is known to all, from all, and to none from none.” (De divinis nominibus, 7.3.)
Undoubtedly inspired by Plotinus who says of the absolute One, that it is “beyond being,” ὑπερόντως and transcended the intellect. (Ennead 6.8.14) For Plotinus it is impossible entirely to comprehend the absolute One with the intellect, “Mind [νοὸς] enhances the divine quality of the Soul [ψυχή], as father and as immanent presence; nothing separates them but the fact that they are not one and the same, that there is succession… What the Mind must be is carried in the single word that Soul, itself so great, is still inferior." (Ennead 5.3.3) Mind must be inferior to the One because it is compounded for it contains a multiplicity of Ideas and the One is free of composition, “Mind stands as the image of the One.” (Ennead 5.1.7.) As Clark explained,
“These Ideas, however, this Divine Mind, is still not the highest principle of all. For in this realm duality remains. Since the Ideas are distinct from each other, there is multiplicity. In knowledge there is always a subject and a predicate, a knower and an object known, and hence duality. But duality is secondary to unity. Therefore it still remains to climb the steep ascent of heaven to the source, the One.” [Gordon Clark, Hellenistic Philosophy. Appleton-Century-Crofts: New York, 1940, pp. 229, 230.]
For the Neo-Platonist, composition implies contingency, and imperfection, because the One is the Good and the Beautiful, the first principle. (Ennead 5.1.1.) Clement of Alexandria seeks to go further than Plotinus, and says God is “above unity and surpasses the One,” δὲ θεὸς καὶ ἐπέκεινα τοῦ ἑνὸς καὶ ὑπὲρ αὐτὴν μονάδα. (Paidagogos, 1.8.) As Clement says elsewhere, “God is not in darkness or in place, but above both space and time, and qualities and objects. Wherefore, neither is he at any time in a part, either as containing or contained, either by limitation or by sections.” (Stromata 2.2) God may be known by direct experience through participation in his energies but his essence remains foreign to us. This is a participation in the life of God, not an intellectual affirmation of some set of propositions, Basil of Caesarea explained,
“The operations are various, and the essence simple, but we say that we know our God from His operations, but do not undertake to approach near to his essence. His operations come down to us, but His essence remains beyond our reach.” (Epistle 234)
The incomprehensibility of the divine essence would mean that it is absurd to try and comprehend the essence of God by the intellect, therefore, Gregory Nazianzen says “reasoning counts for little in knowledge of God,” οί μέν λογισμοί μικρόν είς γνώσιν θεού. (Carmina Moralia, 37.) Because no created intellect can comprehend the divine essence, those passages which ascribe a unique knowledge of God to Christ were used as evidence of the deity of Christ. John Chrysostom says,
“As then many have seen Him in the mode of vision permitted to them, but no one has beheld His Essence, so many of us know God, but what His substance can be none knows, save only He that was begotten of Him. For by knowledge He here means an exact idea and comprehension, such as the Father has of the Son. For he says, “As the Father knows me, even so know I the Father” [John 10:15] and in another place, “Not that any man has seen the Father, save He which is of God.” [John 6:46] Wherefore, as I said, the Evangelist mentions the bosom, to show all this to us by that one word; that great is the affinity and nearness of the Essence, that the knowledge is nowise different, that the power is equal. For the Father would not have in His bosom one of another essence, nor would He have dared, had He been one among many servants, to live in the bosom of his Lord, for this belongs only to a true Son, to one who has much confidence towards His Father, and who is in nothing inferior to Him.” (Homiliae in Evangelium Ioannis, 15.2)
To any created intellect the divine essence is totally invisible, and unknowable, even to the holy angels Chrysostom says “to them His essence is invisible.” (Ibid.) Christ says in John 5:37 “And And the Father who sent me has himself borne witness to me. His voice you have never heard, his form (είδος) you have never seen.” Of this passage Theophilus of Antioch says, “His form (είδος) is unspeakable, expressible, since it is invisible to human eyes.” (Ad Autolychum 1.1-17) Likewise, John of Damascus says after quoting John 1:18,
“The Deity, therefore, is ineffable and incomprehensible. For no one knows the Father, save the Son, nor the Son, save the Father.” [Matthew 11:27] And the Holy Spirit, too, “so knows the things of God as the spirit of the man knows the things that are in him.” [1 Corinthians 2:11] Moreover, after the first and blessed nature no one, not of men only, but even of supramundane powers, and the Cherubim, I say, and Seraphim themselves, has ever known God, save he to whom He revealed Himself.” (Expos. Fidei 1.1)
The appearances of God in the Old Testament were harmonized as visions of the pre-incarnate Christ temporarily taking a visible form, or as appearances of angelic beings, Chrysostom again says.
“It is to declare that all these were instances of (His) condescension, not the vision of the Essence itself unveiled… He prepared them from old time to behold the substance of God, as far as it was possible for them to see It; but what God really is, not only have not the prophets seen, but not even angels nor archangels. If you ask them, you shall not hear them answering anything concerning His Essence.” (Homily 15.1)
Therefore, on the traditional eastern model, the persons of the Trinity have full knowledge of the essence, because the Trinity knows himself. But for the created intellect, it is impossible for God’s essence to be known directly, His properties may be known but his essence may not, hence knowledge of God can be obtained indirectly by two general methods.
By contemplation of the λόγοι of the creation which manifests him.
By direct experience of his uncreated energies (ενεργεία) which means to participate in the life (ζωή και βίος) of God.
The distinction between the essence of God and his properties, commonly called the Essence and Energies Distinction (EED) became a standard feature of Eastern Orthodoxy after the Palamite Controversy. These ideas were given formal exposition in the Councils of Constantinople of 1342, 1351, and 1368. But if I were to talk about the syntheses of Maximus the Confessor and Gregory Palamas directly, this would become a very lengthy discussion indeed.