The purpose is life, that is, that our mortality would be swallowed up by life. The gift of the Spirit functions as the guarantee, the downpayment, of our future resurrection. So, Paul concludes in verse 5 where he started in verse 1. We know that we will have a resurrection body in the future. We are assured of this because we have the Holy Spirit. No matter how happy your life is now, you still long for something better. We all naturally think how life could be better. There is a longing in us for perfection. There is a sense of incompleteness and an ache in our lives. We are not fully satisfied or fulfilled. We sense that there is more to life. Those desires are not a bad thing. They remind us that we were made for another world. They remind us that this world is not our home. They point us forward to the resurrection.