[O]ne of John’s purposes in writing his gospel was to deal with this question of the integrity of monotheism in Christian faith, as it arose internally within the Christian community and as it was also raised from without by Jewish critics.
We may note parenthetically that this same question is raised in Justin Martyr’s Dialogue with Trypho. Justin devotes the entire middle section of his dialogue (chaps. 48-108) to the justification of the Christian practice of worshipping Christ. This parallel is especially interesting because Justin’s conversion to Christianity probably occurred in Ephesus, and, according to Eusebius, the conversation with “Trypho” on which the dialogue is based also took place in Ephesus (cf. Johannes Quasten, Patrology [Westminster: Newman Press], 1 [1950], pp. 197, 203-03). I the Fourth Gospel was also written at Ephesus, then the Dialogue with Trypho might reflect the same type o Jewish opposition to Christianity in this same area some years later.
John deals with this problem by showing that the Son, although one with the Father, is at the same time subordinate and obedient to the Father. Once he states this view directly by stating that the Father is greater than the Son (14:28). But usually he prefers to describe this aspect of the relationship in dynamic rather than abstract terms. He emphasizes, for example, that the Son does nothing on his own authority (5:19, 30; 7:18, 28; 8:28; 12:49); the Son does not seek his own glory (8:50, 54); he does not speak his own words (14:10, 24); he does not give his own teaching, but the teaching from God (7:16). Positively, on the other hand, the Son does what is pleasing to the Father (8:29); the Son honors the Father (8:49) and glorifies the Father (7:18; 17:1, 4); he keeps the commandments of the Father (12:50; 14:31; 15:10; 18:11); he does the work of the Father (4:34) and seeks the will of the Father (5:30; 6:38). In these ways John expresses his conviction that the Christian belief in the unity of the Son and the Father is not a violation of monotheistic faith. He does not seek to give a rational explanation that would dissolve this paradox, but through his description of the actions of the Son he expresses his belief that the unity of God’s own will and purpose is not violated.
We should note further two characteristics of the way John treats this relationship between the Son and the Father. First, he frequently weaves together the themes of unity and subordination in the same passage, indicating in this way that they must be seen in close inter-relationship with one another. For this reason it is not sufficient simply to isolate and list the themes, as we have done above. Such an analysis is helpful for appreciating the variety of ways in which John expresses these themes, but we must also recognize how closely he weaves them together. An illustration is the discussion of Jesus’ “works” in 5:17 ff., which occurs after Jesus has healed a man on the Sabbath. Jesus justifies his actions by saying, “My Father is working still, and I am working” (5:17). The Jews understand this as a claim to equality with God (v. 18). Jesus’ reply in verses 19-24 opens with the theme of obedience and subordination but passes almost imperceptibly into the complementary theme that the Son has a unique relationship to the Father, who loves him, shows him all his own works, and bestows on him the functions of giving life and passing judgment. By relating the themes so closely in this way John implies that neither one can be fully understood apart from the other.
A second characteristic of the way John presents the relationship between the Son and the Father is that a given phrase may actually refer to both aspects of the relationship. Here again we see that it is somewhat misleading to list various passages separately, as we have done above. The statement that the Father has sent the Son, for example, occurs quite frequently throughout the Fourth Gospel. This seems to mean primarily that the Son has a special and unique relationship with the Father—the Son, and no other, was sent by the Father in this way; the Father, and no other, was the one who sent the Son. But the phrase also suggests that the Son fulfils his role through obedience and subordination to the Father—the Father sent the Son with a mission to perform, and the Son does the will of the Father by accomplishing the mission on which he was sent. Here again we see how closely John interrelates the two aspects of the relationship between the Father and the Son and indicates that the one cannot be understood fully apart from the other. (Philip B. Harner, The “I Am” of the Fourth Gospel [Philadelphia: Fortress Press, 1970], 54-55)