In a previous post, I explained Dietrich Bonhoeffer’s idea of “religionless Christianity” primarily in terms of its institutional structure, such as the absence of the church. Here I try to explain the concept itself, while admitting that it still puzzles me. Bonhoeffer elaborated the concept of religionless Christianity in the two years before his murder by Hitler’s Gestapo, and it was undeveloped at the time of his death. I think it remains a puzzle for which we have, at best, no more than half the pieces.
Religionless Christianity is based on “a world come of age,” which began with the Enlightenment (early eighteenth century). Even before then, the Western world found less and less need for the “God hypothesis,” as Bonhoeffer calls it (Letters, pp 325, 360). Every thinker from Machiavelli to Hobbes to Galileo, and every discipline from science and technology to medicine and law, created worlds with no place for God. In some ways this is good, for in a world come of age people take responsibility for their own fates, instead of blaming God.
Basics of Bonhoeffer. Dietrich Bonhoeffer was not a systematic thinker, and I’ve had difficulty finding the themes that connect his thought. One problem is that his early writings, such as The Cost of Discipleship, differ from his latter writings, especially his Letters and Papers from Prison, written in the two years between his arrest and murder by the Gestapo when his link to the plot to assassinate Hitler was uncovered. 
Religionless Christianity. (Bonhoeffer post # 2)