“… but Christ is all, and in all.” (Colossians 3:11)
In strong contrast (“but”) to the human distinctions just enumerated (v.11a) Paul makes the amazing assertion that “Christ is all, and in all.” Paul closes with a phrase which is void of a verb (“is” is added to make sense of it in English), but is all the more powerful for its succinctness. The proper noun (“Christ”) is placed at the end of the sentence for emphasis. Christ is said to be “all, and in all.”
Just what is meant by saying Christ is “all”? The neuter plural form in Greek serves to encompass all things. Robertson says that it is used as a predicate for “Christ” and thus stands “for the totality of things.” Christ created all things (1:16a). Christ sustains all things (1:17b). Christ is supreme over all things (1:17a). Christ is “all.” This is not a pantheistic statement, but a way of saying that the sum and substance of everything is Christ. He is the singular point of their origin. He is the one necessity for their continuance. All things exist for Him (1:16b). It is then both logical and appropriate to speak of Christ as “all.” In the application of God’s grace, then, Christ engulfs all racial, religious, cultural, and cultural differences with His indiscriminate grace. “Christ is all” anyone needs to become a fully welcomed and functioning participate in the “new self” (v.10). Nothing added. Nothing needed. “Christ is all.”
Paul speaks here of this as an established fact. Yet he speaks elsewhere of it as a fact (in the universal, all-inclusive sense) yet to be established. “When all things are subjected to Him, then the Son Himself also will be subjected to the One who subjected all things to Him, so that God may be all in all” (1 Cor. 15:58). Indeed, even here in Colossians he does so: “He is also head of the body, the church; and He is the beginning, the firstborn from the dead, so that He Himself will come to have first place in everything [or “in all”]” (1:18). What Christ is now He is by divine and redemptive right. Yet this is not currently seen and acknowledged by all. At His return, however, all will see what has always been true of Him – “Christ is all, and in all”!
As sweeping as is the first part of this statement, this is not all that Paul asserts. He adds (“and”) that Christ is “in all.” In the Greek adjective (“all”) by form may be either neuter (‘in all things”) or masculine (“in all [redeemed] people”) plural. The first would be a pantheistic statement, something Paul would not make. Surely then it is the latter and Paul is emphasizing that Christ now indwells His people through His Spirit (John 14:16-18). He has made His people His temple, both individually (1 Cor. 6:19) and corporately (1 Cor. 3:16). Elsewhere Paul speaks of God as “Father of all who is over all and through all and in all” (Eph. 4:6). Now the fullness of God (Christ) has come to fill us full of Himself (Col. 2:9-10) and to be in us and to us and for us all that we should be. Indeed, our calling is to be “His body, the fullness of Him who fills all in all” (Eph. 1:23)! This will not be fulfilled by straining effort to achieve such a standing. It is achieved by Christ as He indwells His people who in restful faith simply find Him to be their all in all. This cannot be restricted by any distinction found among mankind—be it cultural, racial, religious or social. “Christ is all, and in all”!
 Robertson, Grammar, 657.