A seminary professor once told me that all of theology is in the prepositions. This is mostly true. Take the Nicene Creed, for example. The second clause concerns the person and work of our Lord Jesus Christ. It is the first half of that clause with which we are concerned.
And in one Lord Jesus Christ, the only-begotten Son of God, begotten of the Father before all worlds, Light of Light, very God of very God, begotten, not made, being of one substance with the Father; By whom all things were made.
I recently heard someone quoting the creed incorrectly. He was intending to quote from the original creed from the council of Nicea when he said: “God from God, Light from Light, very God from very God.” That tiny change of preposition makes all the difference. When we say “Light of Light,” the first is not contingent upon the second. This is a statement of identity. Were we to say “Light from Light,” the first is contingent upon the second. The two are not the same; the first is lesser than the second.
When we say “Very God of Very God,” we are making a statement about the self-existent God existing in a multiplicity of persons. When we say “Very God from Very God,” we are saying only the second is self-existent; we are saying the second preceded the first; we are saying the second is the source of the first; we are saying our Lord Jesus Christ is a created being.
A contingent being owes its existence to something else. My existence is contingent upon my parents; upon the people who employed my father; upon the farmers who grew my food; upon the truckers who transported my food; upon the supermarket that sold my food; upon the government that provided basic infrastructure; etc. I am not a self-existent being. My life is not my own.
The bible tells me that when I see Him, I shall be like Him, for I shall see Him as He is. I shall not be Him, but I shall be like Him. The Orthodox call this theosis; that we shall become gods by grace, but not God in essence. In other words, we shall be god from God, but not God of God.