The center of Paul's theology is the resurrection. It is also the center of our faith because if Christ has not been raised then our faith is meaningless (1 Cor 15:17). If there is no resurrection of Christ then there is no resurrection of believers and death is still the victor! The good news for Paul was that Christ has been raised and that his preaching was not in vain for we will one day be resurrected as well. Really that is the exclamation point on the good news of the gospel.

20 But in fact Christ has been raised from the dead, the firstfruits of those who have fallen asleep. 21 For as by a man came death, by a man has come also the resurrection of the dead. 22 For as in Adam all die, so also in Christ shall all be made alive. 23 But each in his own order: Christ the firstfruits, then at his coming those who belong to Christ. 24 Then comes the end, when he delivers the kingdom to God the Father after destroying every rule and every authority and power. 25 For he must reign until he has put all his enemies under his feet. 26 The last enemy to be destroyed is death (1 Cor 15:20-26, ESV).