Comparison between verses 5 and 6 shows that emphasis in verse 6 must fall on for us, which has no counterpart in verse 5. “Only” is added by Good News Bible to give appropriate emphasis to one.

As Revised Standard Version and Good News Bible show, the stress is on one God rather than on Father. The context also suggests that here Father means much the same as “the Creator” (Good News Bible) and does not have the specifically Christian meaning of “Father of our Lord Jesus Christ.”

The difference of prepositions in for whom and through whom is also in the Greek text. God has made us “through” or “by means of” Christ, and he has made us for himself. For the thought of verse 6a, see Deut 10.17.

Verse 6b and one Lord … may be a quotation from a very early Christian confession. One can translate this as “and we believe that there is only one Lord….” Lord, Jesus Christ, through whom are all things … will need to be rendered in many languages as: “Lord, Jesus Christ, through whom God created all things.”

The clause through whom we exist may be rendered in an idiomatic way; for example, “all we Christians walk our lives through (or, dependent on) him.” Or one may begin a new sentence at this point; for example, “He enables all us Christians to live our lives.”

Verses 5-6 form a single sentence in Greek, as in Revised Standard Version and Good News Bible. Other translations find it more natural to divide the sentence; for example, Parola Del Signore: La Bibbia in Lingua Corrente:
• It is true that people speak about certain divinities in heaven and in earth; and indeed there are many of these “gods” and “lords.” For us, however, there is only one God and Father. He has created all things, and it is by him that we live. And there is one Lord, Jesus Christ, by means of whom all things exist. And we live by means of him.

Quoted with permission from Ellingworth, Paul and Hatton, Howard A. A Handbook on Paul’s First Letter to the Corinthians, 2nd edition. (UBS Handbook Series). New York: UBS, 1985/1994. For this and other handbooks for translators see here .