When I read Bonhoeffer's quote it reminds me of John 3:15,16. Whosoever believes shall not perish. The word believe is better translated " faith in," or " trust." Faith and trust are one and the same thing. The distance between mental assent to abstract truth and trusting Jesus with your whole life is the distance between heaven and hell. This one word, "believe," may have done more damage and caused more people to go to hell than any other thing. The devil himself believes in God, believes in the Son of God, believes in the trinity, believes that Jesus came and died for the sins of humanity, he believe all of that.
It makes no difference whether you believe all of that and more. What makes the difference, what causes a man to be born again from above is having faith/trust in God with your whole life. To surrender your life, to lay it down and give it over, to believe what Jesus said and because you believe it to give your whole life to him, this is salvation. Those who do that then follow Him all the days of their lives. They do not seek to increase the bounty of their nets, they seek first the Kingdom of God and His righteousness and have trust/faith in Him for everything else.................bro Frank