Why is every human being a child of Adam and spiritually dead?
Every human being is a child of Adam because when Adam fell, the entire human race inherited his fallen Adamic nature. Since all people come into the human family through Adam, they share his fallen condition and are spiritually dead. This is why the verse declares that if one died for all, then all were dead.
Les teaches this has been emphasized from day one: when Adam fell, you and I inherited that Adamic nature. Thus every human being who has ever come into the human family is a child of Adam, part of a fallen race, and spiritually dead. Les connects this to the verse in 2 Corinthians where the love of Christ constrains us, because if one died for all—the whole human race—then all are dead. He further stresses that the crucified and resurrected Christ becomes the object of our faith, not the Jesus of Nazareth of His earthly ministry, although He is the same person; our gospel is based on what was revealed after His resurrection and ascension.