'As is the earthy, such are they also that are earthy: and as is the heavenly, such are they also that are heavenly.'
And just like the first man was of the earth, and so produced earthy descendants of similar nature to himself, so is the second man heavenly, and produces heavenly seed of like nature. Those who look to Adam will die. Those who look to Christ have everlasting life (John 5:24). They have passed from death to life. They are, as it were, already heavenly men.