"For it was the Father's good pleasure for all the fullness to dwell in Him, and through Him to reconcile all things to Himself, having made peace through the blood of His cross; through Him, I say, whether things on earth or things in heaven." (Colossians 1:19-20)There is some confusion among the translators as to how to translate this verse. Some, as here, translate it as being the Father's good pleasure that allowed the fullness to dwell in Jesus while other translators, such as Darby, translated this verse this way, "for in him all the fulness [of the Godhead] was pleased to dwell," (Colossians 1:19 Darby) This interpretation acknowledging that it was the "fullness" that both pleasured and dwelt in Jesus Christ. Either way, we are brought to the interesting term of the "fullness" and its indwelling in Jesus Christ.
This Greek word, transliterated as the Pleroma, was not of uncommon use by Paul and other apostolic writers. However, in the first few centuries of the church, there were several heresies that were swirling around during that time that all went under the head of Gnosticism. To those of these heresies, the scriptures were a veritable code book full of the identities of many "gods" and many levels of "gods." To them, the "fullness" was yet another God, separate from the Father and the Son. Similarly, when they read in Genesis, "In the beginning God created the heavens and the earth." (Genesis 1:1) The find the name of another god, "beginning" in whom the creator god (also different from the Father and the Son) performed all his creating. However, while Paul may have used some interesting words, he never wrote in code."For we write nothing else to you than what you read and understand." (2 Corinthians 1:13) Fortunately for us, their error was resolutely refuted and, by the fourth century, this heresy was all but extinct.
What Paul is trying to tell us is that, while Jesus was fully human, he was also fully God. God fully dwelt within Him just as His humanity fully filled Him. This means that, as He suffered as a man he also suffered as God and, as His suffering reconciled us to Him and His humanity, it also reconciled us back to God. Many have tried to explain how this could be and even battles have been waged by those defending their belief against another. However, Paul here presents it simply as a truth with no explanation or defense. We may not be able to understand it but it is nevertheless still true.
Because of sin, mankind and God has been at odds and separated from one another. God is holy and man a sinner and it was his sin that separated him from God. How could mankind be reconciled to God while he stood under the condemnation of the law and under the judgement of death? How could God forgive sin until the righteous requirements of the law had been fulfilled? Sin occurred and the law demanded that its just sentence be executed.
The only solution was for God to come Himself, take our sentence of death upon Himself, and then defeat the law through His resurrection from the dead. Paul put it this was, "because in the forbearance of God He passed over the sins previously committed; for the demonstration, I say, of His righteousness at the present time, so that He would be just and the justifier of the one who has faith in Jesus." (Romans 3:25-26) Jesus was just and, as such, was able to become the justifier of those who believe in Him through His death on the cross and His resurrection from the dead. It took God to reconcile us back to God and that is just what He did,