St.Anselm was agonized over what was the necessity for God to become a human being. 

So He wrote a famous book "Cur Deus Homo" which means "why was God a man?"

 

Christianity through the ages has suffered from the fallacies and heresies regarding the dual nature of Christ. Why it is that? 

The Salvation of Humanity hinges on the true divinity and real humanity of Christ. That is why. God became a man and died a shameful and violent death. It is one of absolute duties for us to study the reason for such a death.

The Apostle Paul found the answer and shared his faith in Gal 2:20 ".. who loved me and gave himself for me...".

He looked at Jesus on the cross and saw that God was there on the cross and realized that God was crucified for him. He did not confess " Who loved us and died for us".

"Cur Deus Homo"