This is not a question that is asked directly in objection to the Gospel, but it is a parallel question that deals with everything we have looked at thus far.
Who did put Jesus on the cross? Was it Judas who betrayed him? Was it the Jews who handed him over to be crucified? Was it the Romans who did the deed? Was it the Father who sent him to die? Or was it Jesus himself who surrendered his life in obedience to the Father's will?
Well, the answer to all these questions is: "Yes" - they are all true. And because they are all true we see something wonderful. The cross may not be the intellectually watertight answer we were looking for, but it is the answer that God gives. In the cross he demonstrates what he is like.
In the cross God demonstrates that he is sovereign over all things and is good and loving even through the suffering and evil that is in the world. He works even the worst evil towards our ultimate good.
In the cross God demonstrates that Jesus is the only way to come to God. He would not have sent his beloved Son to die if there was any other way.
In the cross God demonstrates that he is the Good Shepherd who lays down his life for the sheep.
And in the cross God demonstrates both just how much he hates sin, and just how much he loves us. He sent Jesus to die and take the full punishment for sin in our place.
The cross is God's answer to all our questions. The Apostle Paul when he went to the city of Corinth said, "I decided to know nothing among you except Jesus Christ and him crucified." His answer to all their but-hows and but-whys was always the same: "Look at the cross." He resolved not to reduce the mysteries of God to the confines of his own wisdom and understanding (as considerable as those were), but rather to point people to where they could see the full demonstration of that mystery for themselves.
The only way we will ever get the answers we seek to our questions, is when we grasp the meaning of the cross of Christ.
When we do see it for what it really is, we realise there is another shocking answer to the question, "Who put Jesus on the cross?"...
Accepting Christ died for everyone is one thing, but it's not the same as realising Christ died for me! When I go to the chemist with a sickness, the medicine that the pharmacist hands me may be the same medicine he gives to everyone else, but when it comes over the counter it has got my name written on it. Just so, when I look at the cross, I don't just see Jesus taking the sins of the world. I see God's medicine for my condition with my name written all over it. Jesus hung there for my sin!
This is how Peter addressed the crowds in Jerusalem on the day of Pentecost, who had come from "every nation under heaven":
"Therefore let all Israel be assured of this: God has made this Jesus, whom you crucified, both Lord and Christ."
When the people heard this, they were cut to the heart and said to Peter and the other apostles, "Brothers, what shall we do?" (Acts 2:36-37)
When we realise that we put Jesus on the cross, and he hung there for us, it demands a response.