An affirmation of the cross as part of God's will and purpose for the world.
The death of Jesus, both with regard to its manner and its purpose, was set and determined by God himself. It wasn't a last-minute adjustment to a plan that was going wrong. It always was the plan as the many references and allusions to the cross in the Old Testament make very clear.
To the Christian, this is a thrilling truth because it puts our salvation at the heart of God's will and purpose for this world. For the unbeliever, it reveals the folly of rejecting, not merely a doctrine, but the set plan of almighty God. The death of Jesus on the cross was so meticulously planned by God that, over a period of thousands of years, he alludes to it, and shows us it's going to happen - so that when it does, at last, take place, there should be no doubt as to its meaning. As all this is true; then we had better take it seriously!