This article questions the applicability of traditional Form Criticism to noncanonical gospels. Traditional Form Criticism has relied heavily on assumptions about the evolution of the Jesus tradition which were developed exclusively from observations of the Synoptic Gospels. These assumptions generally relate to the ideological climate in which Jesus materials developed, including issues such as the tradition users' Christology and sense of "history." Because noncanonical gospels developed in contexts of alternate, non-synoptic ideologies, it is unreasonable to presuppose that the surface texts of these gospels developed in ways identical to the development of Synoptic materials. The methodological priority granted to the Synoptic Gospels in NT Form Criticism is described here as "Synoptic Eclipse." This issue is explored by examining Helmut Koester's extensive work on the Gospel of Thomas. It is demonstrated that Koester's consistent advocacy of the value of Gos. Thom. is hindered methodologically as Koester is forced to utilize the tools of traditional NT Form Criticism. Koester is typical in this respect of the recent wave of scholars who seek to learn more about the primitive Jesus tradition by examining noncanonical materials.