The notion of Jews and Gentiles standing together as one people might seem less of an impossible dream for us these days. In the time when Paul wrote his letter to the Ephesian church, the idea of Gentiles and Jews identifying as one with each other was pretty much unthinkable.
Paul indicates it is not whether we happen to be one of these or one of those that is important anymore. The critical thing is that Christ came, lived, died and rose again. It is our belief in this central reality that forms the basis of any true desire to follow Christ.
It is Christ who shows us the shape and nature of eternal life - He is the corner stone out from which everything else is built. We are the ones being built (together with others who follow Christ), into a new creation… a new way of being together that is not based on enmity, but is built on grace, love and forgiveness.