Theosis has been taught everywhere, always, in Christendom. It is truly a catholic (universal) teaching.
To answer your question, Psalm 82 is directed to all mankind. We were created with a purpose, to become like Him. This is the entire purpose of the creation of mankind. The fact that in our fallen state we have become something we were not created to be is irrelevant.
In John 10, Christ is using Psalm 82:6 to rebuke the Jews. They objected to His deity; He responded by saying that the Psalm that "gods" refers "to whom the word of God came". Has the word of God come to you? Has it come to me? Has it come to the whole world, gentiles and Jews alike? Christ's teaching is clear - that psalm applied to all that the word of God had come to, and now it applies to all men. This is the good news!
We were created in His image and likeness.
You are not understanding theosis, you are taking it too literally. He is the Existing one, there is no other God, we do not become God. His Essence is always beyond us. But, we become like Him, as St Maximos says, we ascend to our prototype, and become conformed to Him like wax to a seal (cf Romans 12:2).
The ultimate salvation is to become gods by Grace what He is by Nature, as Romans 5:2 tells us "we exult in the hope of the glory of God". I quoted from 2 Peter, we partake of the divine nature - and so become commingled with the divine, and become like God. Not just Holy as an absence of evil, but Holy like He is Holy. Not just not-dead, but alive, because He is alive. We share in His divinity. Phil 1:6 says that ultimately the work of perfection will be completed, we will become perfect.
To answer your question, Psalm 82 is directed to all mankind. We were created with a purpose, to become like Him. This is the entire purpose of the creation of mankind. The fact that in our fallen state we have become something we were not created to be is irrelevant.
In John 10, Christ is using Psalm 82:6 to rebuke the Jews. They objected to His deity; He responded by saying that the Psalm that "gods" refers "to whom the word of God came". Has the word of God come to you? Has it come to me? Has it come to the whole world, gentiles and Jews alike? Christ's teaching is clear - that psalm applied to all that the word of God had come to, and now it applies to all men. This is the good news!
We were created in His image and likeness.
You are not understanding theosis, you are taking it too literally. He is the Existing one, there is no other God, we do not become God. His Essence is always beyond us. But, we become like Him, as St Maximos says, we ascend to our prototype, and become conformed to Him like wax to a seal (cf Romans 12:2).
The ultimate salvation is to become gods by Grace what He is by Nature, as Romans 5:2 tells us "we exult in the hope of the glory of God". I quoted from 2 Peter, we partake of the divine nature - and so become commingled with the divine, and become like God. Not just Holy as an absence of evil, but Holy like He is Holy. Not just not-dead, but alive, because He is alive. We share in His divinity. Phil 1:6 says that ultimately the work of perfection will be completed, we will become perfect.