That the Father is the one God is important to know, for scripture reveals it; but it is important to know not only that these words are true, but what those words mean according to the scriptures. How, after all, can the Father be the “one God” (1 Cor. 8:6), while the Son is also called God (Jn 1:1)?
To answer this question it is important to understand what the term “God” even means in itself. It is a term used very frequently throughout the scriptures, not only for the Supreme God, the Father, the “Lord God Pantokrator” (Rev 4:8), but also for beings as low as men and angels. As Jesus noted in John 10:35 “He [God] called them gods, to whom the word of God came”, speaking of a psalm where the men of Israel were called “gods”. In Psalm 82:1 “God stands in the congregation of the mighty; He judges among the gods”, calling created angels gods. Paul is well aware of this when he writes “For even if there are many called gods, whether in heaven or on earth (as there are many gods and many lords), 6 yet for us there is one God, the Father, of whom are all things, and we for Him; and one Lord Jesus Christ, through whom are all things, and through whom we live.”
Scripture then presents the word “God” as something which may be ascribed to many persons. What’s more, scripture treats the word “God” as a relative word, denoting relation rather than some absolute quality. Thus all throughout scripture we have statements where phrases like “my God”, “your God”, and “our God” are used. Sir Isaac Newton comments well on this point:
“This Being [God] governs all things, not as the soul of the world, but as Lord over all: And on account of his dominion he is wont to be called Lord God Pantokrator [Greek word usually translated “Almighty”], or Universal Ruler. For God is a relative word, and has a respect to servants; and Deity is the dominion of God, not over his own body, as those imagine who fancy God to be the soul of the world, but over servants. The supreme God is a Being eternal, infinite, absolutely perfect; but a being, however perfect, without dominion, cannot be said to be Lord God; for we say, my God, your God, the God of Israel, the God of Gods, and Lord of Lords; but we do not say, my Eternal, your Eternal, the Eternal of Israel, the Eternal of Gods; we do not say, my Infinite, or my Perfect: These are titles which have no respect to servants. The word God usually signifies a Lord; but every lord is not a God. It is the dominion of a spiritual being which constitutes a God; a true, supreme, or imaginary dominion makes a true, supreme, or imaginary God.” (Newton, General Scholium)
Newton’s observations well account for how scripture uses the term “God”. To be “God” therefore is to have dominion, and Godhood is dominion. Thus scripture can justly call the judges of Israel and holy angels “gods” without this in any way blaspheming the one supreme God, the Father. That the Father is the one God then does not tell us something about His nature, but rather tells us that He is the one Who alone has supreme dominion over all, absolutely. Thus on the one hand, as Paul and other scriptures said, there are many gods, and yet in another sense, the highest sense, there is only one God, the Father of the Lord Jesus Christ, Who alone has dominion over all things absolutely. This dominion (or Godhood) extends not only over all creation, but also over His own only-begotten Son, as we saw above. Thus Christ could say to His disciples, looking forward to His ascension “I ascend unto my Father, and your Father; and to my God, and your God.”
That the Son, although He is another individual person from the Father, the one God, is also called “God” should be no surprise at all. For the Lord said “All authority has been given to Me in heaven and on earth” (Matt 28:18). Having thus received Godhood over all creation from His Father, “in Him the fulness of deity dwells in bodily form” (Col 2:9). And thus the Son is called “Mighty God” (Isa 9:6), and thus the Psalmist says to the Son “Thy throne, O God, is for ever and ever: the sceptre of thy kingdom is a right sceptre. 7 Thou lovest righteousness, and hatest wickedness: therefore God, thy God, hath anointed thee with the oil of gladness above thy fellows.” (Ps 45:6-7 KJV).
The Son is then truly ‘God’ or ‘a God’, but this does not make Him the Lord God Almighty, the one God, the only true God- for these titles belong to His Father alone, as His Father alone has Godhood over all things absolutely, including over the Son Himself; while the Son has Godhood over all creation, given to Him by the Father, which He exercises according to the Father’s will, on His behalf (John 5:30).
Godhood then is dominion, not a nature, and to be “God” is to have this dominion. For Christians then there is one God, the Father, the one Supreme Ruler over all, and His Son is also God, because the Father has given Him a share in that dominion over all creation, while the Son Himself is still subject to the Father as His God.
Scripture then uses the term “God” as a term for an individual possessing dominion, without respect to the metaphysical nature or essence of that person. And in the case of the Father, Who is alone the Supreme God over all, “God” is frequently used as a name denoting His office. Just as King Richard, a monarch, may simply be referred to by His subjects as “the King”, and may simply be addressed as “King” as a name, yet “King” is used that way because of Richard’s office, not because “King” has become his proper name. Similarly in the case of the one God, the Father, Who is the Monarch of the universe, He is frequently called simply “God” as a name, and referred to by scripture without further qualification as “the God”, not because “God” is the proper name of the Father, but because it denotes His role as the one Who possesses supreme dominion (Godhood) over all.
Thus in scripture when the term “God” is used as a name for an individual without qualification, it nearly always refers to the Father, “the Lord God Pantokrator”, the Supreme God. We see this usage throughout the scriptures, for instance in John 3:16: “For God so loved the world, that He gave His only-begotten Son, that whoever believes in Him shall not perish but have eternal life.” In that verse it is clear that the person denoted by “God” is the Father, although there is no term in addition to God denoting that. That is because the default usage of the term “God” as a name, biblically, is in reference to the one God, the Father of the Lord Jesus Christ.
And thus also God can reveal His proper name and speak of His name being the unutterable tetragrammaton, for “God” is not His proper name, but a title denoting His Supreme Godhood over all (Jer 32:18).
This understanding is an important basis for any discussion of theology or the Trinity. Without knowing what we mean by the term “God” and what it means for there to be “one God”, and without knowing what “Godhood” is, we cannot hope to accurately evaluate theological statements concerning the Trinity.