It is not a false statement to affirm that there is no "default context of 'o theos'". There is no default meaning of a word. Each usage has to be understood by the context in which it was used. You incorrectly assume that there is a "default context of 'o theos'" and this leads you to deny that "o theos" is applied to Jesus and to invent grammar that contradicts your assumptions.It is not a false statement to aver that the default context of "o theos" is the Father, and all other contexts exceptional. You are making a false statement if you aver anything else.
In the case of John 20:28, if "o theos" is a default reference to "the Father" then an additional modifier "my" or "your" cannot change the usage to another referent. It would be enough to say "o theos" is always a reference to the Father. However, that is not accurate because "o theos" isn't used exclusively for "the Father" in the New Testament. The next thing would be to realize that the modifiers "my" or "your" can (again, if one doesn't hold the assumption that "the default context of 'o theos' is the Father") change the relationships between the terms, but it doesn't always. Imagine the phrase "o theos mou" spoken by Nebuchadnezzar compared with the same statement spoken by Daniel. Now imagine the same statement made by Peter and Paul. The change of the referent is on the basis of context not grammar, because you know that the God of Daniel, Peter, and Paul is different from that of Nebuchadnezzar. The grammar is the same, but the referent changes based upon context.
You are making statements about the grammar that aren't accurate, and you are making incompatible arguments.
Jesus is/was just as capable of speaking of a false god using "o theos" as anyone else is/was. "Default context" doesn't exist.As to the primary usage of "o theos" by Jesus, it involves a personal context which is the default context. Here "o theos" always defers to his Father.
It shouldn't be worthy of comment. But you still don't understand it, so here we are. There exists no "default" usage of "theos". That faulty assumption is unique to you, in this discussion at least.It's not even worthy of remark when theos is used of a false god. This is so obvious that it doesn't require elucidation or remark.
Again, since the meaning of the term is based upon context one has to look at the situation in which the statements were made. Jesus/the word was first called "theos" while he was with God. When Jesus became a man it is clear that he was no longer God in the same sense that he was before. After his resurrection, it is unclear exactly what Jesus is, and this is the situation when Jesus spoke with Mary and Thomas. To claim that the each of these usages must mean the same thing in these different contexts requires evidence. It can't be disregarded on the basis of an assumption.There is another context besides the purely personal context which is the doctrinal context, e.g. John 10:34-36, which explains the way in which the Father delegates his authority. He invests his authority in others besides himself, and confers divine recognition upon them, not because they are inherently divine (they may, or may not, originate from heaven), but because they have been imbued (even if temporarily) with the Father's authority. For men, this is the Hebrew Elohim context. The YHWH context is mostly a personal relating to the Father (e.g. Ps 110:1), but can involve angels / heavenly agents as intermediaries. In this respect the Word functions/governs as YHWH, but the title belongs to the Father. Of himself, as man originating from heaven, Jesus explains this doctrine as including himself as "God's Son." This is official doctrine even per John 10:36.
The doctrinal context does not violate the personal context. Rather it is an extension to it.
It can be applied to "the Father" or "the Son" or "the Holy Spirit". As far as I can recall, I've never used the term "equally", but that would be acceptable considering that they are all God and don't cease to be so solely because they aren't in focus.You have not "corrected me" but eviscerate all such biblical distinctions, when you pretend that the title "o theos" can be applied equally to the Father, or to the Son or to the Holy Spirit to the exclusion of the Father.
What is nonsense is your apparent belief that the presence or absence of an article necessarily changes the referent of "theos". Passages like John 1:18 "Θεὸν οὐδεὶς ἑώρακεν πώποτε· μονογενὴς θεὸς ὁ ὢν εἰς τὸν κόλπον τοῦ πατρὸς ἐκεῖνος ἐξηγήσατο." and even John 10:33 "ἀπεκρίθησαν αὐτῷ οἱ Ἰουδαῖοι· περὶ καλοῦ ἔργου οὐ λιθάζομέν σε ἀλλὰ περὶ βλασφημίας, καὶ ὅτι σὺ ἄνθρωπος ὢν ποιεῖς σεαυτὸν θεόν." make it clear that the absence of the article alone does not change the referent. (And it shouldn't need to be said that the case a word is in doesn't matter.)This much is assinine nonsense. In fact I don't believe there is a single instance in the entire Greek NT where Jesus or the Holy Spirit is alluded to as "o theos", apart from where the article is used to force a vocative in the LXX Greek translation of a Hebrew passage that itself does not contain the article (Heb 1:8), and which refers in the Hebrew to Elohim (not YHWH - Ps 45:6). As I have pointed out, the LXX could just as well have translated the Hebrew Elohim here by the Gk kyrios. There is nothing in this usage which violates anything I have said above.