What did Paul mean by "so also is Christ" when he compared Christ to a human body?
Paul meant that just as a human body is one unit with many members, so the body of Christ is one living organism made up of many different believers. Though they differ in background, culture, and status, all who are saved by the same power and gospel are one in Christ.
Les explains that only Paul spoke of the body of Christ, and in verse 12 Paul uses the human body as an illustration. The human body is one but has many members—hands, feet, eyes, ears—and all operate as one from a central nervous system and a central place of thinking. In the same way, “so also is Christ” refers to the body of Christ: many different people—rich and poor, black and white, from around the world—with their own cultures, yet if saved by the same power and the same gospel, they are one in Christ. Les illustrates this by saying believers could go to the Philippines or anywhere and feel at home with born-again children of God because they are one in Christ. This body is not merely an organization but a living organism, and verse 13 goes on to address how one enters it.