The necessary starting point of preaching

As I have been preparing to preach from John 6, I have been amazed at the deeply trinitarian picture that Jesus presents in the work of salvation. Not long after glimpsing that, I read Newbigin on trinitarian preaching, and found him to be immensely helpful:

But it is also significant that, when one goes out side of the 'Christendom' situation to bring the gospel to non-Christians, one soon discovers that the doctrine of the Trinity is not something that can be kept out of sight; on the contrary, it is the necessary starting point of preaching. Even in the simplest form of missionary preaching, one finds that one cannot escape dealing with this doctrine. . . .

Thus even in its most elementary form the preaching of the Gospel must presuppose an understanding of the triune nature of God. It is not, as we have sometimes seemed to say, a kind of intellectual capstone which can be put on the top of the arch at the very end; it is, on the contrary, the arche, the presupposition without which the preaching of the Gospel in a pagan world cannot begin. (Weston, Paul. "Lesslie Newbigin: Missionary Theologian." Grand Rapids, MI: Eerdmans. 2006 p83, 84)