He explains that because the human has been given the gift of freedom within limits, and because we recognize the paradox of that state of being, humans are anxious. We are tempted to deny the limitations of our knowledge by maintaining the illusion that we are in control. The ideal possibility is that faith in the ultimate security of God's love would overcome all immediate insecurities of nature and history. He is also anxious because he does not know the limits of his possibilities. He can do nothing and regard it perfectly done, because higher possibilities are revealed in each achievement.
All human actions stand under seemingly limitless possibilities.
There is therefore, no limit of achievement in any sphere of activity in which human history can rest with equanimity. The story of the temptation of Jesus illustrates what Niebuhr was getting at. In Matthew's gospel, Jesus had come directly from his baptism in the Jordan to his retreat in the wilderness where he wandered alone, contemplating his mission. Jesus was anxious. The precondition for temptation was there.