In order to infer from Scripture that Christ is ὁμοούσιος (homoousious)[one is being]with God the Father, you have to pick certain texts of Scripture as the standard in light of which the others are to be interpreted. So, for example, Jesus says that the Father is greater than Himself (John 14:28), and that regarding “that day and hour” no one knows, not even the angels of heaven, nor the Son, but the Father alone. (Matt 24:36) He also said, “Why do you call Me good? No one is good except God alone.” (Mark 10:18) He says that He will ascend “to my Father and your Father, to my God and to your God.” (John 20:17) In 1 Cor 1:24 St. Paul says that Christ is the “wisdom of God.’ But of wisdom, the Proverbs say, “The Lord created me at the beginning of his work, the first of his acts of old.” (Prov. 8:22) Even Jesus Himself refers to Himself as “the beginning of God’s creation” (Rev 3:14). That’s one possible way of interpreting ‘begotten’ in John 3:16 and elsewhere, and “first-born” in Col 1:15, as though God brought forth Christ as the first of His works, and then Christ became that through which all other things were made. And that’s one way of interpreting what St. Paul says in 1 Cor 8:6, where he writes, “yet for us there is one God, the Father, from whom are all things and for whom we exist, and one Lord Jesus Christ, through whom are all things and through whom we exist.” And St. Paul says that the head of Christ is God (1 Cor 11:3), and implies that when all things are subject to the Son, then the Son will also be subjected to God. (1 Cor 15:28)
If a person picks those passages as the passages by which the other Christological passages are to be interpreted and understood, one will not arrive at a Nicene Christology. On the other hand, if one picks other passages implying Christ’s divinity as the interpretive key for the passages listed above, then, given the aid of a concept from Greek philosophy (i.e. ούσιος) one can arrive at something close to a Nicene Christology. But Scripture itself does not state which set of texts are to be the hermeneutical key by which to interpret the others.
This idea was very helpful to me in understanding exactly how different traditions get very different doctrines from the same scriptures. As a protestant I could not see it. If scriptures taught Catholic doctrines then why didn't Calvinists see them? Some passages are obscure but most seem quite clear. Lots of Calvinists were reading the bible from cover to cover. They were not consciously trying to read the bible like Calvinists. They were honestly trying to hear God speak through His word. Why did they not arrive at Catholic doctrines?
The idea of interpretive keys was very helpful. To start with a few passages as the definitive description of something and approach the others with that truth in mind. I could see how one could arrive at very different answers that way. Those answers would not change simply by re-reading scripture. It was a difference in the way you organized scripture into doctrine. This wasn't a wrong thing to do. But it was something that needed to be done right and scripture itself did not tell us how to do it.
For example, if you talk to a Calvinist in justification they will normally start with a few verses in Romans and maybe a couple in Galatians. Why start there? Because their tradition tells them those are the key texts on justification. What if we started with the story of Zacchaeus instead(Lk 19:1-10)? Then you would have a very different doctrine. Zacchaeus wants to see Jesus. Jesus invites Himself to Zacchaeus' house. Zacchaeus responds by offer to make restitution for his sins. Jesus replies with a declaration that salvation has come and Zacchaeus is a son of Abraham.
It is important to understand that we cannot avoid these interpretive keys. They are not always wrong. But if you get them wrong you can end up very firmly convinced you are right when you are not. Remember these key texts are in scripture so nobody is going to convince us that taking the plain meaning of scripture is ever going to be a problem. Then when we go to the "problem" texts we say, "let scripture interpret scripture" meaning we need to see these texts in the light of our key texts.