Imagine two different groups of scientists. One group, armed with a set of encyclopedic guidebooks which are constantly being annotated, take turns to look at a distant star or galaxy through an extremely powerful telescope. The scientists offer comments from what they see, and in the light of what they see, or deduce, further annotations are made in the guidebooks, and their deliverances are passed on to anyone who is interested. The other group of scientists is standing round the rim of a huge concavity in the surface of the earth, or maybe there are in submarines, gazing at the rim of a huge concavity which has been detected as giving form to the sea bed. They are trying to work out what has happened, what force, what dimensions, what speed, produced this impact, and what the consequences have been, or are, or will be, for life on the planet as a result of whatever it was that produced this concavity.
Of the two groups of scientists, the one which offers the closer analogy to the discipline of theology is the second group. For the discipline of theology, a distinctively Christian discipline, presupposes a happening, an impact, an interruption, having already happened, and offering a shape which can be detected as the consequences of its having happened spread further. Furthermore, it presupposes that that happening, that impact, is not only a blind collision, of the sort produced by a meteor in the vicinity of the Yucatan peninsula, but is an act of communication. This means that the theologian is not merely an outsider, commenting about something having happened, but is on the way to becoming part of the act of communication from the inside. Is on the way to becoming a shock wave from the impact, which is part of the impact itself.
-James Alison, Undergoing God, page 1.