Consistent with the Old Testament teaching on light and darkness outlined in my previous post “The Old Testament Background to the Concept of Light and Darkness in John’s Gospel”, the Gospel of John clearly identifies Jesus of Nazareth as being the spiritual light of the universe.
For John, Jesus is “the light of humanity” (John 1:4). The allusions in John 1:1–5 to Gen 1 (“in the beginning” in vv. 1–2; “word” in vv. 1–2; the act of creation in v. 3; life in v. 4; light and darkness in vv. 4–5) suggest that just as the word of God brought about the existence of physical light at the beginning of the history of the world, in a similar way the Word of God (who is Jesus) is the spiritual light that brings safety and life into our world of darkness (John 1:4). By Jesus coming into the world, his light has shone into the darkness; and wherever his light has reached, there the darkness has irresistably been overcome (John 1:5). At the same time, however, there are evildoers who love the darkness rather than the light, who as a consequence refuse to come to the light (John 3:19–20). In the original context, this is a reference to those Jews who were viewed as having broken the covenant with God. On the other hand, those (Israelites) who do the truth (i.e., who are committed to the covenant with God) come to the light of Christ in order to show the genuine value of their obedience to God under the Mosaic covenant (John 3:21).
John’s Gospel strongly promotes the idea that Jesus is “the true light who illuminates all people” (John 1:9). Jesus has shone in the world in order to enlighten people, regardless of nationality. He has “come as a light into the world, in order that everyone who believes in him might not abide in the darkness” (John 12:46). Thus, Jesus himself claimed to be “the light of the world” (John 8:12; 9:5). Following Jesus and his teaching is to avoid “walk[ing] in the darkness,” and results in a person experiencing “the light of life” (John 8:12). It is important to walk in the daytime rather than at night. Walking in the daylight is equated with seeing “the light of this world,” the benefit being the avoidance of stumbling (John 11:9–10). Consistent with the use of this imagery in the Old Testament, the person “who walks in the darkness does not know where he is going” (John 12:35). The danger with not seeing where you are going is that you will stumble so as to fall away from the pathway of salvation. Jesus viewed his earthly ministry as the short period of time (“a little while”) in which “the light is among you” (John 12:35; see also John 9:5). He called upon the Jews of his day to “believe in the light” while the light was still among them, “in order that you might become sons of light” (John 12:36). Rejecting the light would result in the Jewish nation being overtaken by darkness (John 12:35).
John’s Gospel is also concerned to make the point that John the Baptist, when compared with Jesus, is definitely “not the light”; instead, he only bore testimony concerning the light (John 1:8). At the same time, however, Jesus acknowledges that John the Baptist was “a lamp that burns and shines,” and that the Jews “were willing for a time to rejoice in his light” (John 5:35). John the Baptist was a light, but not the light. The “true light” who came into the world, “who illuminates all people,” is none other than Jesus of Nazareth. In him the Old Testament prophetic expectation of the coming of the glory of Yahweh has been fulfilled.