Windfish,
With respect, and in order:
- You said: “I cannot understand what it means that the Cross was a sacrifice. Well, how does the death of the Christ relate to the satisfaction of sin? There is a causal link there that I think has not been explained.”
It is not the cross per se - it was the entire Passion - man’s rejection of him, whipping, beating, mocking, crucifixion. Many have a tendency to collectively refer to all of these injuries as “the cross”.
There is no causal link between the death of Christ and the “satisfaction of sin”. Sin was not being “satisfied” by Christ’s suffering: the debt that resulted in man “being in the red” to God because of man’s sins were being satisfied. Keep in mind that the Church teaches us that God views creation as having and needing a “balance”. We can’t continually go into debt and never repay - to do that would lead to hell. But ONE thing that could not be repaid was the harm done to God when man FIRST disobeyed God. THAT harm was infinite and could only be “satisfied = repaid” with an infinite repayment. How could that be accomplished to benefit man, but where it was impossible to be done BY man? By God becoming incarnate. God, through his Son, repaid the debt incurred by man as a result of man’s original sin. Note the baseball/window example I gave above: saying “sorry” is not enough - the window still needs to be repaired to bring back “order” before the break of the window.
- You said: “And why is a sacrifice even necessary?”
It was NOT necessary in the sense that the way God chose was the ONLY way that God could have considered the harm repaid. God could have done whatever He wanted. But he had a two-fold purpose in Jesus’s death: (1) repairing an infinite harm with an infinite sacrifice - the horrible tortuous death of his only Son, and (2) demonstrating, THROUGH that tortuous death, just how much God loved man.
So it was not necessary in the sense that it HAD to be done (as in, “that was the ONLY way”). It was done simply because God CHOSE that way for the redemption.
- You said: " Did not the Jews atone and plead for forgiveness long before Jesus arrived? Why was it necessary to go beyond that? And is not the sacrifice a bit barbaric? The Jews sacrificed animals, but a human???"
Again, man could NEVER have accomplished a sacrifice never on par with the harm done to God because man inflicted an infinite harm on an infinite being and man, alone, can never do anything that has infinite value. Thus, it took man AND God combined as Christ.
The Jews tried to atone for their sins, but even with Jesus’s arrival, they rejected him. How God chooses to deal with the Jews is between God and the Jews. I make no statement/judgment on that.
And yes, what Christ did WAS barbaric - crucifixion was, at that time, a method of death perfected by the Romans as the most painful way someone could be put to death - slowly, in horrible pain, suffocating for hours (some lasted days on the cross - this explains Pilate’s surprise at hearing Christ died so soon after he was nailed to the cross).
- You said: “And IF the Cross of Christ is efficacious so that the world is restored to before the Fall, why is that we still have concupiscence? Why is there still natural evil? So what does the Cross actually accomplish?”
The world was NOT restored to the same as before the Fall. Man’s chance to be at one with God - that is, the gift of immortal life in both body and soul with eternal bliss - was forever loss with original sin. That would never be recovered. Christ’s Passion was efficacious in the sense that it reopened heaven, without which, no matter how much man would have cooperated with his own salvation, he would have never made it to heaven.
Recall the VERY OLD term “Limbo of the Fathers” - it is where those such as Abraham, Moses, Elijah, Jeremiah, et al., were waiting until Christ came. It is to them, and others, that Christ journeyed after his death to announce what he had just done (“preached to the captive souls”). We call that state of one’s soul (not an actual place) “purgatory”.
“Natural evil” (as you call it) and man’s inclination towards sin exist because God permits them to exist. That is the workings of free will combined with allowing Lucifer to live and battle for men’s souls. God did not and does not cause evil - but he allows evil to exist because if he did not, then man would be denied the greatest gift a man has: the free will to do as he pleases. God does not prevent men from coming to him - he allows men to prevent themselves from coming to God.
Hope this explains it a little better . . . I tried my best.