Translator and scholar Daniel A. Wallace notes quite clearly in his Greek Grammar that "there is an exalted Christology in the Fourth Gospel, to the point that Jesus Christ is identified as God (cf. 5:23; 8:58; 10:30; 20:28, etc).(1) Wallace is a Trinitarian but does identify John 10:30 to be a text which identifies Jesus as God. It is only in post-Biblical history and discussion that a full Trinitarian system and interpretation came about. After hammering away many years the Trinitarian interpretation finally emerged and this text began to be used to support such doctrine. It is a matter of Scripture and not necessarily history that decides what is said here though.
The Good Shepherd:
In John 10 we read of the Good Shepherd and the Sheep. In John the miracles of Christ preface a discussion about the person of Christ. The work of Jesus, while on earth, created discussion about His identity. Early in this chapter Christ is the Door (See also John 14:6) to the sheepfold and at the same time the Good Shepherd (John 10:3, 8). The Jews then desire a public statement from Jesus perhaps to entrap him. At any rate, he does not give them a direct answer. In 10:25 Jesus tells them that the things he has been telling them all along have been pointing to the fact that He is the Christ.
Christ even tells the Jews that His sheep listen to his voice (10:27) and that He gives them eternal life. Jesus gives eternal life? Wait. No mere mortal gives eternal life. No finite person is able to give such an infinite gift. Only God gives such life. Only God can give such a saving life that is efficacious for an infinite number of believers. God gave life to Adam and Eve. Therefore, He is the source of life. Jesus also says that the sheep will never be destroyed and no one can snatch them from his hand (10:28). No finite person is able to be guarantor of any such thing.
Early Jesus also makes an important distinction when he says that the Father is greater than all. Yet, Jesus also says I and the Father are one. John has already showed us that the Logos was "with" God and yet "was" God. The distinction between Father and Son are not in their being or in their person but in mode of existence. The distinction between the Father and Son is not produced by divine essence but as a result of the humanity of Christ. Jesus then says no one can snatch the sheep from the Father's hands either. No one or anything can snatch a believer from the hand of God. As noted earlier, it is no small matter for Jesus to suggest that no one can snatch believers from His own hand. This is so because Father and Son are the Good Shepherd. It is important to consider the Old Testament background such as Isaiah and the minor prophets to interpret the "I am" sayings. Isaiah 40:11 records:
Like a shepherd He will tend His flock, In His arm He will gather the lambs And carry them in His bosom; He will gently lead the nursing ewes. (Isa. 40:11)The Shepherd of Isaiah is the same Shepherd of John and therefore the very context proves that the hand of the Father and the hand of the Son are one and the same. This further supports the "I am" sayings of Jesus as being connected with the same "I am" statements of Yahweh in the Old Testament (see Exodus 3:13-15; John 8:24; 58, etc) In Rev. 21:22 John's doxological praise of Jesus knows hardly any distinction. In Rev. 21:22 God and the Lamb form one subject using a singular verb. Therefore, to say that God and the Lamb are one and the same is not bad grammar.
As noted earlier in John 10:30 a plural verb ("are") is present. It is not surprising that a plural verb is used here. A plural verb is actually necessary. In the context of John 10 we read of Jesus and the Father. It is Jesus and the Father who are one. Jesus is also the one mediator who John is convinced is both of God and man. The word one here is in the neuter form. It would seem appropriate to have a masculine form here given the nouns Jesus and Father are masculine; however, such is not the case. Trinitarian scholars will suggest that the masculine form would prove the Father and Son are the same person. This is to admit however that gender cases identify person. If so, the masculine form is used in Gal. 3:20 and we could conclude that God is one person.
Plural of Identities:
A plural of identities could be seen here but not necessarily a plurality in person. In this very chapter Jesus is the door of the fold, the Shepherd, the doorkeeper and the Lamb of God. Even here Jesus has a plural of identities but not of person. Jesus then utters the simple but important words, "I and the Father are one." (NASB) Six words. Here Jesus does not say "I am the Father." There was more to be said and John does not gloss the distinction between Father and Son. Nor does it say that Jesus and the Father "share" one essence or that Jesus and the Father merely share a close fellowship as God to man.
Quite clearly the Shepherd is one person and is referred to as one person. The "one" in John 10:30 appears to have a meaning of absolute oneness. There is only one flock, one shepherd and we have already seen He is spoken of as a "He" (Isa. 40:11). The one flock is in Jesus' hand and in the Father's hand. The one flock cannot be in two places at once. So the Father's hand and the Son's hand must be the same place. If they both have the same hand, then they must both be the same person.
Here "hand" in the feminine form is used. It seems to be used figuratively but hand does not simply mean control or power. If so, then there would be two shepherds (if the Father and Son are two different persons). That would also set itself against what Jesus and the Old Testament had already said namely that there is only one Shepherd (John 10:16; Isa. 40:11).
Jesus makes at least seven "I am" statements that serve as descriptions of himself as the Son who makes the Father visible to the mortal eye. He is the Logos--God's self-revelation or self-expression (See John 1:1). In John 10:11 Jesus emphatically states, "I am the good shepherd." Jesus does not have in mind a general shepherd feeding the flock of a hillside. Here there is emphasis--"the good shepherd.". Jesus is the Good Shepherd.
1) Wallace, D.A. (1996) Greek Grammar Beyond the Basics (267) Zondervan Grand Rapids, MI
2) Morris, Leon (1974) The Lord from Heaven (105-106) Intervarsity Press, London
3) Brown, Colin (1986) New International Dictionary of New Testament Theology. Zondervan Grand Rapids, MI