As with any subject of theological significance, viewed in the context of a Jewish-Christian discussion, two perspectives are relevant to our discussion. The first perspective from which the subject of God the Father can be addressed is that of the relationship between ancient Judaism and the teachings of Jesus and of the New Testament in general. The obvious issue here is to what extent the teachings of Jesus are of a kind with contemporary Jewish teaching, what in the background of ancient Judaism is relevant to a proper understanding of the words of Jesus, and to what degree a new teaching can be discerned in his words. Methodologically, such analysis belongs properly to the field of history of religions. A completely different angle on the issue emerges from the perspectives of theology and of interfaith dialogue. While Jews and Christians may not be able to agree upon the second and third persons of the Christian Trinity, the person of God the Father would seem to be the dimension of God that unites Jewish and Christian understanding and that could thus provide a common theological ground. From the perspective of these disciplines, one would therefore want to ask to what extent Judaism and Christianity share a common concept of "God the Father."
That both perspectives come to mind upon presentation of the topic is not accidental. There is a continual movement of interdependence between the philological and historical studies, on the one hand, and the theological articulation of faith, on the other. While in theory there are two different disciplines, asking two distinct sets of questions, in reality the two disciplines feed upon one another. Exegetical and historical insight feed theological positions. The other direction of the hermeneutical circle is that theological positions determine presentation of historical and textual data, thus reading ancient texts into later theological structures. Because of the multiple perspectives that are relevant to a discussion of God the Father, I shall address both perspectives in my discussion. The present discussion thus has the double nature of a historical study, relating to the Gospels in the context of ancient Judaism, and a theological interfaith exercise, attempting to grapple with perceived commonalities and differences between Judaism and Christianity. Of course, once Judaism and Christianity are discussed, we can no longer limit ourselves either to rabbinic literature or to the New Testament, and insights must be drawn from later developments of both traditions. Therefore, in discussing the wider theological and interfaith dimensions of the subject, I shall expand the scope of the discussion to include certain features of later Judaism and Christianity.
Having said this much we have already moved on to the next point on my agenda: spelling out the methodological obstacles on our path. The historical part of my discussion, namely, the relationship between Jesus' concept of God the Father and that of early Judaism, is fraught with methodological difficulties. The confusion of historical and theological method is a major obstacle in the present context. So much has been written concerning the novelty of Jesus' teaching of God the Father. This novelty can be presented either as the totally new proclamation of the previously unknown notion that God is Father, (1) or, in a more subtle version that highlights the new elements that characterize Jesus' understanding of the Father, in relation to earlier Judaism. (2) While such statements ought, methodologically, to be founded upon purely historical study, such study is hopelessly informed by a theological perspective that totally breaks down the kind of methodological rigor that would be necessary to establish the de sired historical truths. Let me begin with a blatant example, and leave the more subtle case of the great Joachim Jeremias to a later point in our discussion. …