There is a need for our being alive at this time on earth. And being confident of this, I know that I shall remain and continue with you all for your progress and joy of faith. Here is the reason God had Paul upon earth. Paul had no mere desire to dangle around on the frayed edges of existence. It is not enough just to live a long time.
Purpose gives life meaning and definition.
Confidence serves our orientation to life. We need to develop towards maturity in our faith. Some believers are baby Christians. A baby's mind and body have not developed yet. A new or static believer remains at a low level of development.