At present we do not have a clear understanding of the historical process through which the existing Vinaya materials came into being. One of the most noteworthy points in this field is the difference in structure between Theravada Vinayas and the Mahasamghika Vinaya. It is thought that the compilation process of the Vinaya may be clarified by explaining the reason for this difference. On this point, scholars such as Frauwallner, Hirakawa, Yinshun, Clarke and myself have presented various theories. Clarke's theory, the most recent addition to the discussion, rejects the thesis of Frauwallner's famous work. If Clarke's criticisms are correct, then his interpretation is a revolutionary contribution to the study of the Vinaya. However, there is a serious logical contradiction in Clarke's theory, and therefore Frauwallner's theory cannot be dismissed. In this article, I will outline these past theories and point out the problems in Clarke's work.