There is only one God, because there is only one Father. The person of the Father alone is the one identified by scripture as the one true God. “Yet for us there is but one God, the Father, from whom are all things and we exist for Him; and one Lord, Jesus Christ, by whom are all things, and we exist through Him.” (1 Corinthians 8:6 NAS). “There is one body and one Spirit, just as also you were called in one hope of your calling; 5 one Lord, one faith, one baptism, 6 one God and Father of all who is over all and through all and in all.” (Ephesians 4:4-5 NAS). And the Lord Jesus Christ, praying to His Father said “This is eternal life, that they may know You, the only true God, and Jesus Christ whom You have sent.” (John 17:3 NAS).
So we can know with certainty from scripture’s plain statements on the matter that the one God of the Christian faith is the person of the Father in particular, although the other two persons of the Trinity, the Son and Holy Spirit, also share the Father’s divine nature. Thus the Nicene Creed begins by confessing “We believe in one God, the Father Almighty…”. Likewise, we may see from their own writings that this was the normal view of the orthodox fathers of the ante-nicene and nicene eras (for a list of quotes see here).
Yet even once the fact that the Father is the one God is accepted and believed as the clear teaching of scripture, the genuine believer may still be left with questions as to why this is the case. How, after all, can the Son and Spirit both be God, possessing the very same divine nature as the Father, and yet not be second and third Gods? If we say that it is because They are the same person as the Father, we have denied the clear teaching of scripture that the Father, Son, and Holy Spirit are three truly distinct persons. There is thus not one God, according to scripture, because there is only one divine person, as there are three persons, yet only one God.
So then, why do the Son and Holy Spirit not constitute second and third Gods in addition to the Father, Who alone is the one God? The answer to this question is multifaceted. The person of the Father alone is the one God because He alone is the ‘uncaused Cause’ and ‘Head without a head’. Additionally, we may point to the unity of the Son and Spirit with the Father in respect to both their essence and their relationship to Him as reasons why They cannot be said to constitute second and third Gods.
To answer these questions and thoroughly explain each aspect of the answer I just gave, I hope to complete a five-part series on this blog, of which this is the first installment. The next four installments planned are: