For as in Adam all die, even so in Christ shall all be made alive.
In Adam all - in union of nature with Adam, the representative head of mankind in their fall.
In Christ shall all - in union of nature with Christ, the representative head of mankind in their recovery. The seed of life brought in by Christ is co-extensive with the seed of death brought in by Adam. All sinned in Adam; all rise in Christ, (cf. Romans 5:12, etc.)