Hardly less crushing was the blow delivered to the Tübingen theories by the genuine Clement and Ignatius. If the theories were correct, certain phenomena should have been observable in these letters. In point of fact, not merely is none of these phenomena to be observed, but what is to be found is so contradictory of what to be expected as to raise the question whether any of these phenomena were ever at any time found in the Christian world.The above is a wonderful example of critical realist thought in action. We have a hypothesis about early Christianity, one presented to us by Baur and the Tübingen school: that into the second century Pauline and Petrine Christianities remained fundamentally opposed and unreconciled. We have a derivative of this hypothesis: the Johannine tradition is the result of a rapprochement between Pauline and Petrine Christianity, and thus must have originated significantly later than the early part of the second century. These hypotheses allow us to anticipate finding certain matters in the relevant data, and not finding others. We should, for instance, anticipate some evidence of tension between Pauline and Petrine Christianity, and little to no evidence of synthesis between the two. Preferably, we would probably want to be able to situate 1 Clement and Ignatius respectively as either Pauline or Petrine. We should, for instance, anticipate finding little to nothing that looks like Johannine material. The difficulty for Baur and Tübingen is that what we should expect on their hypothesis is not there, and much that we should not expect is. Paul and Peter are remembered as co-labourers in 1 Clement. Johannine material abounds in the letters of Ignatius. Etc.
This is the heart of what Lonergan means by "appeal to the data." We have defined the question: to what extent does Baur's hypothesis adequately apprehend early Christian development? In answering that, we have not simply pitted our own countervailing hypothesis against him, but rather asked whether or not his hypothesis can withstand the data. In this case, we have found that the hypothesis does not withstand. We have found that to be the case because we had defined what we should expect in the data if the hypothesis be true, and discovered that the opposite was the case.
Appeal to data is particularly crucial in a discipline as hoary as New Testament studies. All too easily one can substitute disciplinary common-sense for careful attention to the data. For instance, one might state that the canonical gospels report the destruction of the temple, when of course careful attention to the data reveals that in fact they report prophecies about the destruction of the temple (empirically not quite the same thing). Or--a pet peeve of those who work in or even just read contemporary synagogue studies--one might repeat the old absurdity that there is no evidence of synagogue buildings in the first-century Galilee. Such hypotheses, however well anchored they might be in the disciplinary consciousness, are dashed hopelessly against the rocks of data by the waves of attention.