Why is Christ the culmination if Adam was the first federal head of the human race?
Adam was the first federal head of the human race in the natural order, but Christ is the culmination because Scripture's pattern is first the natural, then the spiritual. Paul teaches that what is spiritual did not come first; Adam represents the natural, while Christ represents the spiritual completion of God's purpose.
Les teaches that Adam was the first federal head of the human race, but Christ now becomes the culmination. This is because the Bible deals not only with the physical but with the spiritual. The consistent rule of thumb all through Scripture is first the natural, then the spiritual: first Cain, then Abel; first Ishmael, then Isaac; first Esau, then Jacob; first King Saul, then King David. Paul's text, verse 46, says that which is spiritual was not first. So Adam comes first as the natural head, and Christ follows as the spiritual culmination.