Ephesians 1:23 is sometimes offered as proof that Jesus is the Supreme Being with the assertion that Jesus Christ is the fullness of him who fills all. In some vague manner it is thought that this assertion means that Jesus is God Almighty. Actually, Ephesians 1:23 does not say that Jesus is the fullness of him who fills all, although if one should read it that way, it still would not mean that Jesus is the Supreme Being.
Ephesians 1:22 - He [the God and Father of Jesus -- Ephesians 1:3,17] put all things in subjection under his [Jesus'] feet, and [the God and Father of jesus] gave him [Jesus] to be head over all things to the assembly [the church, the saints],
Jesus did not call himself to the position of headship of the Church but was appointed to it by God. "No man takes this honor on himself." -- Hebrews 5:4.
Ephesians 1:23 - which is his [Jesus'] body, the fullness [completeness, plenitude] of him who fills [accomplishes] all in all.
This could be read several different ways.
"Which" is referring back to the church [the saints]; "his" refers to Jesus. The body of Jesus is made up of the church.
"The fullness" could be seen as referring to the church; "of him" could be referring to Jesus (or God).
"The fullness" could be referring to either Jesus' fullness or God's fullness, although this would hardly fit the context.
Nevertheless, Christ is the bond of unity to his Church -- Christ is in each individual, and each individual in Christ. Each member has been grafted into the true Vine, though in different places. Each member has some function in the mystical Body. All were reckoned in Jesus when he died, and rose, and entered the Father's presence. In him each member has access into the grace wherein they stand. The gift of Christ, on the other hand, has been made to each one of these, that he might realize himself through all the experiences of his members. God provided four Gospels to reveal to the church (not to the world in this age) who and what Jesus Christ is; nevertheless,all believers are required to set forth and exemplify to the world all the excelling glories of Emmanuel. It is for this reason that we are told that the Church is his Body, "the fulness [completeness, full development, plenitude, Greek pleroma, Strong's #4138] of him who fills [brings to completion, consumates, accomplishes, Greek, pleero, Strong's #4137] all in all." -- Ephesians 1:23.
It was Jesus himself who said: "The glory which you have given me, I have given to them; that they may be one, even as we are one; I in them, and you in me, that they may be perfected into one." (John 17:22,23) Due to the covering of Jesus' righteous blood, in such radiance the Church already now stands before God. He sees her essential unity. Its denial does not disintegrate it. Its obscuration does not impair it. The very members of the Church that compose the unity may be unaware of it, and may denounce each other; but even so, the twelve stones are in the same breastplate and the twelve loaves stand side by side on the same table. The members of a large family of boys and girls may dispute with each other, and may be scattered far and wide over the world, but to the mother, in her daily and nightly prayer, there is but one family, and to her they seem sheltered still under the wings of her brooding love.
Jesus himself gives us an illustration: "Most assuredly I tell you, unless a grain of wheat falls into the earth and dies, it remains by itself alone. But if it dies, it bears much fruit." (John 12:24) The "much fruit" owes all its prospects to that one grain of wheat. Possibilities of bread inherent in the one grain of wheat. That one grain of wheat is not of itself a harvest. The "much fruit", is the full development of that grain of wheat, and indispensable if it would realize its possibilities. So also with Christ. The church's all is in him, as he declared, "apart from me (or severed from me) you can do nothing." (John 12:24) The hand is of no use severed from the body; it will simply corrupt. Jesus illustrated this well in his picture of the vine; "Remain in me, and I in you. As the branch can't bear fruit by itself, unless it remains in the vine, so neither can you, unless you remain in me." (John 15:4) "If a man doesn't remain in me, he is thrown out as a branch, and is withered." (John 15:6) The life is in the vine, and only in the vital union with the vine can the branch bear fruit. And yet in this same picture we have a seed thought for the Apostle's other declaration that the Church is the full development of the Christ. It is the branches that bear the fruit. True, the fruit is not their own, but the fruit of the vine, for the life in the branches is the life of the vine, yet in order that the vine may express its life fully in fruit bearing, the branches have their part to play. The branch is only a channel for the expressing of the one life, not a life of its own; but the life of the vine. And the member of the Body of Christ is only a channel for the expressing of the one life, not a life of his own that he is living in the power of the spirit, as Paul said of himself: "I have been crucified with Christ, and it is no longer I that live, but Christ living in me." So it is of the Christ, it is not because of any inherent value in any member. It is simply the extended operation of the Christ life that makes the Church, which is his Body, "the full development of him who accomplishes all [these things, Greek panta] in all [Greek, pansin]."
What we do not find in Ephesians 1 is any thought that Jesus is the Supreme Being; indeed, throughout, Jesus is distinguished from God. Additionally, God is not exalted to higher position of power by another, but it is God who exalts Jesus to such great power.