Rauschenbusch was a key figure in the Social Gospel and single tax movements that flourished in the United States during the late 19th and early 20th centuries.

Though he went through a youthful rebellious period, at age 17 he experienced a personal religious conversion which "influenced [his] soul down to its depths."

[26] In this book, he explains that Christians must be like the Almighty who became man in Jesus Christ, who was with everyone equally and considered people as a subject of love and service.

[28] Rauschenbusch's work influenced, among others, Martin Luther King Jr.,[29] Desmond Tutu,[30] Lucy Randolph Mason,[31] Reinhold Niebuhr,[32] Norman Thomas,[33] George McGovern,[34] James McClendon,[citation needed] and his grandson, Richard Rorty.

Rauschenbusch's view of Christianity was that its purpose was to spread the Kingdom of God, not through a "fire and brimstone" style of preaching, but by the Christlike lives led by its members.

"[37] In Rauschenbusch's early adulthood, mainline Protestant churches were largely allied with the social and political establishment, in effect supporting such practices as the use of child labor and the domination of robber barons.

Whoever sets any bounds for the reconstructive power of the religious life over the social relations and institutions of men, to that extent denies the faith of the Master."

Concerning the social depth and breadth of Christ's atoning work, Rauschenbusch wrote: "Jesus did not in any real sense bear the sin of some ancient Briton who beat up his wife in B. C. 56, or of some mountaineer in Tennessee who got drunk in A. D. 1917.

Solidarity explains it.These six "social sins" which Jesus, according to Rauschenbusch, bore on the cross: Religious bigotry, the combination of graft and political power, the corruption of justice, the mob spirit [being "the social group gone mad"] and mob action, militarism, and class contempt – every student of history will recognize that these sum up constitutional forces in the Kingdom of Evil.

"[40] He believed that the social gospel would be "a permanent addition to our spiritual outlook and that its arrival constitute[d] a state in the development of the Christian religion",[41] and thus a systematic tool for using it was necessary.

In A Theology for the Social Gospel, Rauschenbusch wrote that the individualistic gospel had made the sinfulness of the individual clear, but it had not shed light on institutionalized sinfulness: "It has not evoked faith in the will and power of God to redeem the permanent institutions of human society from their inherited guilt of oppression and extortion.

"[42] This ideology would be inherited by liberation theologians and civil rights advocates and leaders such as Martin Luther King Jr.

This was done at first by the early church out of what appeared to be necessity, but Rauschenbusch called Christians to return to the doctrine of the Kingdom of God.