the synoptic tradition2. Isolated units grow, accumulate, and cluster together. Materials in isolated and clustered form join the stream of traditions, are sustained by it, and in turn increase the momentum toward even larger and more complex formations. One can readily form a mental picture of Bultmann’s model of the synoptic tradition as a steady process of aggregate growth. 1.3 If one presses the question as to the motivating causes of the gospel composition, Bultmann gives a twofold answer.