If immediate experience cannot prove or disprove the miraculous, still less can history do so. Many people think one can decide whether a miracle occurred in the past by examining the evidence ‘according to the ordinary rules of historical inquiry’. But the ordinary rules cannot be worked until we have decided whether miracles are possible, and if so, how probable they are. For if they are impossible, then no amount of historical evidence will convince us. If they are possible but immensely improbable, then only mathematically demonstrative evidence will convince us: and since history never provides that degree of evidence for any event, history can never convince us that a miracle occurred. If, on the other hand, miracles are not intrinsically improbable, then the existing evidence will be sufficient to convince us that quite a number of miracles have occurred. The result of our historical enquiries thus depends on the philosophical views which we have been holding before we even began to look at the evidence. This philosophical question must therefore come first.
Here is an example of the sort of thing that happens if we omit the preliminary philosophical task, and rush on to the historical. In a popular commentary on the Bible you will find a discussion of the date at which the Fourth Gospel was written. The author says it must have been written after the execution of St Peter, because, in the Fourth Gospel, Christ is represented as predicting the execution of St Peter. ‘A book’, thinks the author, ‘cannot be written before events which it refers to’. Of course it cannot—unless real predictions ever occur. If they do, then this argument for the date is in ruins. And the author has not discussed at all whether real predictions are possible. He takes it for granted (perhaps unconsciously) that they are not. Perhaps he is right: but if he is, he has not discovered this principle by historical inquiry. He has brought his disbelief in predictions to his historical work, so to speak, ready made. Unless he had done so his historical conclusion about the date of the Fourth Gospel could not have been reached at all. His work is therefore quite useless to a person who wants to know whether predictions occur. The author gets to work only after he has already answered that question in the negative, and on grounds which he never communicates to us. – from Miracles: A Preliminary Study (1947)