'The Father is greater than I'
'The Father is greater than I' beside 'I and the Father are one' — equality and subordination in the Trinitarian controversies, Arianism included.
John 14:28
28You heard how I told you, ‘I go away, and I come to you.’ If you loved me, you would have rejoiced, because I said ‘I am going to my Father;’ for the Father is greater than I.
John 10:30
30I and the Father are one.”
What each tradition says
Rabbinic / Midrashic
Kohler and Krauss say that equalizing the Son with the Father marks an innovation in Pauline theology. They cite 1 Cor. 8:6, which speaks of one God, the Father, and one Lord, Jesus Christ, through whom are all things.
Kaufmann Kohler (1843-1926) and Samuel Krauss (1866-1948), The Jewish Encyclopedia, vol. 12, s.v. 'Trinity' (New York: Funk & Wagnalls, 1906) — opening paragraph on the dogma's development
Patristic
Augustine explains that there is no contradiction: in reference to the servant-form, the Son of God says, “The Father is greater than I”; in speaking of the form of God, the same Son declares, “I and my Father are one.” They are one because the Word was God, and the Father is greater because the Word was made flesh.
Augustine of Hippo (354-430), Lectures or Tractates on the Gospel According to St. John, Tractate LXXVIII, in NPNF ser. 1, vol. 7 (ed. Philip Schaff, 1888) — Tractate LXXVIII on John 14:27-28, section 2 (against the Arians)
Catholic
Aquinas says these words are to be understood of Christ's human nature, in which He is less than the Father and subject to Him, while in His divine nature He is equal to the Father. Athanasius is cited: equal to the Father in Godhead, less in humanity.
Thomas Aquinas (1225-1274); trans. Fathers of the English Dominican Province (1920), Summa Theologiae, Second and Revised Edition (New Advent) — I, q. 42, a. 4 ('Whether the Son is equal to the Father in greatness'), reply to objection 1 (which cites John 14:28)
Orthodox
Gregory of Nazianzus admits that the Father is greater than the Son in respect of being the Cause. But if someone assumes the Father is Cause by Nature and then concludes He is greater by Nature also, Gregory says it is hard to tell whether they mislead themselves most or those they argue with.
Reformed / Protestant
Calvin says that in John 14:28 Christ is not comparing the Father’s divinity with his own, nor his human nature with the Father’s divine essence. Instead, Christ compares his present state with the heavenly glory to which he would soon be received.
John Calvin (1509-1564), Commentary on the Gospel According to John, vol. 2 (trans. William Pringle; Edinburgh: Calvin Translation Society, 1847) — Commentary on John 14:28
Evangelical
John Wesley explains that the Father is greater than he as he was man. As God, neither is greater nor less than the other.
John Wesley (1703-1791), Explanatory Notes upon the New Testament (1755); CCEL's 'Wesley's Notes on the Bible' — Note on John 14:28