Grow up - is a key part of the message in this part of 1 Corinthians. They have before them situation where Christian brothers are taking each other to court, and for such a trivial matter that should have been very easy for the church to sort out - but they are so immature that they can't even judge the simplest of cases. They are struggling to make right judgements in their immaturity and they need to grow up. Those in Christ should grow to have a mature eternal view point enabling them to easily discern what is right in much smaller earthly matters. The Corinthians are so muddled that they even need reminding of basic things that will keep people out of the kingdom of God. As Paul reminds them, there is a great reminder for us of the grace and generosity of God in his salvation of us which ought to then give us clarity to make right judgements in this world as we wait for Christ to return.