The last chapter was an attempt to survey some aspects of the reasoning of the Fathers in doctrinal debate. But the aspect of their thinking which is most directly linked to the question of the development of doctrine is the way in which new ideas arose and were related to existing beliefs. Disputants about the theory of development have debated in what sense, if any, it is proper to speak of the emergence of new ideas at all. With this broader issue we need not now concern ourselves. It is self-evident that there was in some sense an emergence of new insights, whether in the ultimate analysis they are to be regarded as new revelation or new understanding of the old. The question which I wish now to investigate is the historical question how such new insights were assimilated and related to old ideas and formulations of belief.

There are two main ways in which new beliefs can be incorporated into an existing body of ideas. The most natural initial assumption is that all that is required is simply to add in the new beliefs without any modification or alteration of those already held. If this can be satisfactorily done, no problem arises. But very often the new belief does not conveniently fit into the existing pattern of ideas. In that case the new beliefs cannot simply be added in; they have rather to be added on as a series of awkwardly attached appendices.