In an article in The Regent World (Winter 2010, Vol 22, Number 1), Professor Rikk Watts says the following.
Ancient rhetoricians were designers, seeking to persuade people of a different vision for the polis. Since it did not exist, they could not prove it — how do you “prove” a dream? But if you’ve seen the movie Invictus you will understand what is involved. You need to know your audience, their history and their culture. You need to know what they value and you need to use metaphors, since metaphors are the essential bridge between the known and the unknown… [Then] it dawned on me that the Bible itself is fundamentally rhetorical.
Marketplace theology is about precisely this: incarnational “rhetorical” God-speak. His word to us is brimming with metaphors, history, ethics and vision. It is God’s rhetoric, persuading us to join him in his new creational work for a new and glorious future. It is a divine summons to design in the light of his life-giving truth.
The more I study Paul, the more I realise the rhetorical character of his letters. They are letters—speeches!—that seek to persuade. The Bible is not about a set of otherworldly (so-called) ‘spiritual principles’. It is not a set of systematic theological propositions. The biblical authors did not write the Scriptures to prove the existence of God per se (for they took for granted that he existed). Instead, the Bible is God’s revelation to humankind about who he is and his saving acts. And we are called to embody the gospel in our daily life. That is, we are to be incarnational “rhetorical” God-speak’, as Watts says. In doing so we bear witness to Christ.