St John the Evangelist was the first Christian theologian in whom we find the affirmation that ‘God is light’. He claims that he heard this truth from Jesus Christ Himself: ‘This then is the message which we have heard of him and declare unto you, that God is light, and in him there is no darkness at all’.[1] This phrase is probably one of those logia Iesou (sayings of Jesus) which were remembered by Jesus’ disciples and were partly included into the New Testament, partly into the apocrypha, and partly were preserved for a long time in oral tradition. Of himself Jesus said: ‘I am the light of the world‘.[2] For St John Jesus was the light which ‘shined in the darkness’, the light that ‘lighteth every man that cometh into the world’.[3]

            The theme of God as light was a leitmotif of the entire corpus of writings of St Gregory Nazianzen.[4] The very nature of God in Gregory is most commonly characterized as ‘light’ (fos), and the ‘terminology of light is one of the basic elements of Gregory’s theological language through his entire career as a church writer’.[5] This terminology appears as early as in his Second Discourse, which was delivered after Gregory’s ordination into priesthood: here he says that the angels ‘hardly contain the splendour of God, Who is covered by darkness, for He is light the most pure and inaccessible for most creatures, light which is inside everything and outside everything, which is all beauty and higher than all beauty, which illumines the intellect’.[6] Gregory developed the theme of light in his Ninth Discourse, which he pronounced immediately after his consecration to the episcopate: here he compares God with the sun and claims that for some God is light, while for others He is fire: the one who is not ready to encounter God will be blinded by His light, like children that are blinded by lightning.[7]

            The image of the sun, which derives from Plato,[8] is one of Gregory’s favourite images when he speaks of God.[9] Gregory uses this image in particular when he speaks of the human person’s striving to God as the highest good: 

...From many and great things... which we receive and will receive from God, the greatest and the most generous is our inclination and our kinship to Him. In the realm of intelligible things God is the same as the sun in the realm of sensible.[10] The sun illumines the world visible, while God illumines the world invisible; the former makes bodily sights sunlike, while the latter makes intelligible natures godlike. The sun, while giving a seer to see and a seen to be seen, is itself incomparably more beautiful than what is seen; in the same manner God, while giving a thinker to think and an object of thinking to be thought of, is Himself the climax of everything intelligible,[11] so that every desire finds its end in Him and nowhere else reaches forward. For there is nothing higher than Him... He is the supreme limit of everything desirable, and in Him every contemplation finds its rest.[12] 

            Speaking of God as light, Gregory emphasizes that this light is incomprehensible: it “escapes the speed and the height of the intellect, and always departs to the same degree as is comprehended, and leads higher the one who falls in love with it him by running away from him and, as it were, escaping from his hands’.[13] The theme of pursuit of God, Who always escapes from the human soul, as well as the theme of an endless spiritual progress in search of the incomprehensible God, is characteristic of the entire mystical tradition of the Eastern Church; it is particularly developed by Gregory of Nyssa.[14]

            In Gregory Nazianzen’s Thirty-first Discourse, the trinitarian character of the divine light is emphasized. God the Trinity is light, says Gregory, and every Person of the Trinity is light: 

There was the true Light, which lighteth every man that cometh into the world,[15] that is, the Father. There was the true Light, which lighteth every man that cometh into the world, that is, the Son. There was the true Light, which lighteth every man that cometh into the world , that is, the Comforter.[16] There are three subjects and three verbs - He was and He was and He was. But a single reality was. There are three predicates - light and light and light. But the light is one, God is one. This is the meaning of David’s prophetic vision: In Thy light we shall see light.[17] We receive the Son’s light from the Father’s light in the light of the Spirit: this is what we ourselves have seen and what we now proclaim - it is the plain and simple explanation of the Trinity.[18] 

            The most thorough and systematic treatment of the theme of God as light is found in the Fortieth Discourse, where Gregory speaks of the entire hierarchy of lights beginning from the light of the Trinity. This trinitarian Divine light is absolutely transcendent and is beyond everything sensible, yet it penetrates through all the created world. Everything that exists participates in this Divine light an different levels: 

God is the light supreme, unapproachable and ineffable, which is incomprehensible for the intellect and unutterable for speech, which enlightens all rational nature... I mean the light which is contemplated in the Father and the Son and the Holy Spirit... A second light is the angel... A third light is the human person...[19] I know also of another light, by which the primeval darkness was driven away and pierced: this light was the first of the visible creation to be called into existence; and it illumines the whole universe...[20] 

            Apart from this hierarchy of lights, there are, according to Gregory, other types of light, namely those related to God’s actions in the history of humanity. The entire Bible, the whole life of the Church up to the point when it enters the eschatological Kingdom of heaven are regarded as an unceasing revelation of the Divine light. This revelation is given to some individuals, to an entire people, to all Christians, and - in the future age - to the entire body of those who are saved: 

Light was also the firstborn commandment given to the firstborn man...[21] And a light typical and proportionate to those who were its subjects was the written Law, which prefigured the truth and the mystery of the great Light, for Moses’ face was made glorious by it.[22] And, to mention more lights, it was light that appeared out of fire to Moses, when it burned the bush indeed, but did not consume it.[23] And it was light that was in the pillar of fire that led Israel...[24] It was light that carried up Elijah in the chariot of fire and yet did not burn as it carried him.[25] It was light that shone around the shepherds when the eternal Light was mingled with the temporal.[26] It was light that was the beauty of the star that went before to Bethlehem to guide the wise men’s way and to be the escort of the Light that is both above us and with us.[27] Light was that Godhead that was shown upon the mountain to the disciples...[28] Light was that vision which blazed out upon Paul, and by wounding his eyes healed the darkness of his soul.[29] Light is also the brilliancy of heaven to those who have been purified here, when the righteous shall shine forth as the sun,[30] and God shall stand in the midst of them, gods and kings,[31] deciding and distinguishing the ranks of the blessedness of heaven. Light is also in a special sense the illumination of Baptism... for it contains a great and marvelous mystery of our salvation.[32] 

            We can see that the idea of God as light is the foundation of Gregory’s entire world-outlook and of his vision of history. Gregory is definitely one of the creators of the theology of light, which would later be developed by many great mystics, including Maximus the Confessor, John of Damascus, Symeon the New Theologian, Gregory Palamas. The theologians of Byzantine Hesychasm referred to Gregory Nazianzen as the most authoritative mystical writer who discussed the theme of the divine light. It is significant that the theme of the Divine light was to become central in Eastern Christian mystical tradition after Gregory Nazianzen, whereas the theme of the ‘divine darkness’, so dear to Gregory of Nyssa, remained somehow on the periphery of mystical theology of the Eastern Church.[33]