When Jesus asked Peter in the Gospel of Matthew, "who do you say that I am?" both of them knew that everything was at stake in his answer. Centuries later, in civilized Germany, Bonhoeffer also knew what was at stake in the answer.
“The new situation must be created, in which it is possible to believe in Jesus as God incarnate; that is the impossible situation in which everything is staked solely on the word of Jesus. Peter had to leave the ship to risk his life on the sea, in order to learn both his own weakness and the almighty power of the Lord. If Peter had not taken the risk, he would never have learned the meaning of faith. Before he can believe, the utterly impossible situation on the seas must be displayed. The road to faith passes through obedience to the call of Jesus. Unless a definite step is demanded, the call vanishes into thin air, and if men imagine they can follow Jesus without taking this step, they are deluding themselves like fanatics.” (The Cost of Discipleship, 68.)