John 10:30 I and the Father are one.
John 10:30 is a used by many groups to support their theology and one over which exegetes have spilled much ink. Arians, modalists, Trinitarians, and others have all appealed to this verse to support their theology. Generally, the Arian understanding is that the oneness of the Son and of the Father is a oneness of purpose or will, the modalist claims that the oneness is that of person, the Trinitarian sees the statement of 10:30 as oneness of being.
Of the three, the modalist claim seems to be weakest. The word “one” in this case allows for alternate understandings than just oneness of person. Furthermore, that the Son speaks of the Father (and vice versa) in language that distinguishes them lessens the claim that the Father and the Son are the same person. The strength of the modalist position is that it seeks to maintain a high view of monotheism.
The Arian understanding is better than that of the modalist. The Arian view retains the Father-Son distinction and it is possible that the oneness of purpose and/or will is in mind here, especially since agency functioned that way. Where the Arian view falls short is that it ignores the specific places where deity is ascribed to Christ.
The Trinitarian view often views John 10:30 in light of oneness of being. This is a better understanding than oneness of person in light of the reasons given above. It also accords well with the Jewish claims that Jesus makes himself God (but does not make himself the Father). Within John, and even within Second Temple Judaism, there appears to have been the concept of distinction within God.
In light of John’s Prologue, by which the Gospel appears to have been intended to be read, the opening statement that the Logos was “with God” and “was God” (1:1b,c) lends support to oneness of being, without diminishing the distinctions or denying the Godhood of the Logos. Richard Bauckham’s Christology of divine identity is a helpful model for making sense of the paradox.