In Jürgen Moltmann's Introduction to Christian Theology, he expresses the necessity of the resurrection of Jesus as an event of history. Moltmann believes that the resurrection gave birth to the Church, the Gospels, and the entire Christian faith. Moltmann does not believe that the Christian faith began with the Easter faith of the disciples experienced after the crucifixion of Jesus, as Rudolf Bultmann taught, but instead Moltmann believes that the only plausible explaination for the rise of Christianity, is the historical resurrection of Jesus from the dead.
The efficacy of the Christian faith is dependent upon the reality of Jesus' being resurrected from the dead by God. We have indeed reason to regard the words of Paul in 1 Cor 15:14 seriously: "If Christ has not been raised, then our preaching is in vain and our faith is in vain." With all historical assurance we can say that, save for Easter, there would have been no New Testament letters written, no Gospels compiled, no prayers offered in Jesus' name, and no Church. For at the very heart of the early Church's preaching stands the word about "the Author of life, whom God raised from the dead. To this we are witnesses" (Acts 3:15). Paul says: "If you confess with your lips that Jesus is Lord and believe in your heart that God raised him from the dead, you will be saved" (Rom 10:9). Easter therefore is no mere addendum to other factors in the story of Jesus Christ, nor is it, on the other hand, merely a concept of Christian faith; it is constitutive for the Christship of Jesus and constitutive for the very existence of Christian faith. In thinking of the resurrection we are laying our fingers right on the pulse of the primitive Church's life.
But it is precisely the resurrection of Christ and the resurrection faith which are questionable today. It does not fit into our modern world of things calculable and manipulable. Is the resurrection of Christ an event among other events in our world? Is it only a mythological symbol of a religious language of times past? Are we hopelessly old fashioned with our faith in the the resurrected Jesus? 
Moltmann answers these questions:
My thesis is: Christian faith is resurrection faith or it cannot be Christian faith any longer. The resurrection of Jesus was the historical origin of Christianity and is and must be the essential foundation of any truly Christian faith. My thesis is simultaneously a historical and a systematic thesis. 
[^Header Image Background] Albert Pinkham Ryder [Public domain], via Wikimedia Commons
[^1] Moltmann, Jürgen. An Introduction to Christian Theology. Ed. Douglas Meeks. N.p.: Duke, 1968. 194-5. Print.
[^2] Ibid. 195.
Related: An Introduction to Christian Theology, Historical Resurrection, Jesus, Jürgen Moltmann, Resurrection, Rudolf Bultmann