Did the writer to the Hebrews use the nominative case as a vocative?

[Paidion]

Almost every translation renders Hebrews 1:6 as, "Your throne, O God, is forever and ever." Yet the word "God" is in the nominative case rather than the vocative case. The nominative case is used as the subject of a verb.

The Greek does use the vocative case in addressing God. In Mark 15:34 and Matthew 27:46, it is recorded that Jesus cried out to God, "My God, my God, why have you forsaken me?" In these passages "God" is in the vocative case, the case of direct address.

But in Hebrews 1:6, the word "God" is in the nominative case, the case used as subject. So why isn't it translated as subject?
If it were it would be translated as "God is your throne, forever and ever."

I am aware of only one translation that has "God is your throne" and that is the New World Translation of Jehovah's witnesses. But many dismiss that translation on the ground that JWs reject the belief that Jesus is God. However, it is insufficient to reject their translation on that ground. We need to consider the Greek grammar of the statement. If the writer had meant that God were addressed, then why didn't he use the case of address, namely the vocative case?

[mikew]

I don't have any personal knowledge on this but thought to check a commentary for you. (I forget how much you rely on commentaries.) This may help a little for those curious about the issue you raise.

The Hermeneia makes this observation on Heb 1:8
Although it may have involved an address to the king as god, it is more likely to be construed as a predication, in parallelism with the following verse, to be rendered “your throne is (a throne) of God, eternal.”89 The LXX rendering is ambiguous, since the form used for “God” is nominative. It is, however, possible, even in classical Greek, to use the nominative for the vocative,90 and in the LXX91 and the New Testament this usage is common. That

Attridge, Harold W., and Helmut Koester. The Epistle to the Hebrews: A Commentary on the Epistle to the Hebrews. Philadelphia: Fortress Press, 1989.

It sounds like the parallelism reinforces the vocative reading.

[backwoodsman]

Almost every translation renders Hebrews 1:6 as, "Your throne, O God, is forever and ever." Yet the word "God" is in the nominative case rather than the vocative case.
[,,,]
But in Hebrews 1:6, the word "God" is in the nominative case, the case used as subject. So why isn't it translated as subject?
If it were it would be translated as "God is your throne, forever and ever."

Robertson says it's unclear which case it is, but says either makes good sense. I know nothing about Greek cases, but tend to agree that it works either way.

Vincent says that, while he goes with the vocative, the translation of the Hebrew (Ps 45:6) is doubtful.

The Cambridge Bible points out that, while the LXX doesn't use the vocative, all ancient writers seem to have understood the Hebrew in a way that corresponds to the Greek vocative.

What authority are you following in saying it's nominative?

I am aware of only one translation that has "God is your throne" and that is the New World Translation of Jehovah's witnesses. But many dismiss that translation on the ground that JWs reject the belief that Jesus is God. However, it is insufficient to reject their translation on that ground.

I don't recall hearing that given as the reason to reject the NWT, but it's possible I heard but didn't notice it. I only recall hearing it's because they deliberately inject their beliefs into the text, which seems to me a very good reason. The occasional slip-up by a translator is one thing, but doing it deliberately and systematically to support one's otherwise Biblically unsupportable belief system is intellectually dishonest. The only other translation I'm aware of that does that is Witness Lee's Recovery Version.

[Paidion]

What authority are you following in saying it's nominative?

By the authority of Hellenistic Greek grammar, which I spent a year studying at the Winnipeg Bible Institute, and an additional 3 years of studying at the University of Manitoba, where I received a BSc degree.