Patterson feels that DeConick's work is flawed because she is using form-critical methods in order to engage in literary stratigraphy. In other words, she is setting out the literary history of Thomas by using a method that is designed for work on oral tradition. As Patterson puts it,
Can form criticism be used to identify literary strata? This seems doubtful. Form criticism theorizes about how sayings may be adapted and used in an oral medium to accommodate various situations in the life of a community. But, of course, Thomas is not an oral performance. It is a document that incorporates material from countless prior oral performances in which all manner of development and remodeling has already taken place. That a particular saying in Thomas bears the form critical (i.e., oral) marks of secondary development is not an indication that it represents a secondary development in the literary history of the Gospel as a whole.Patterson's criticism of DeConick on this point may be a little too stark. As I read her, the method is not so much old form-criticism but an attempt to integrate form-criticism, source-criticism and redaction-criticism into a newer model that also takes seriously the rhetorical culture of the emerging Christian movement. She speaks of a "'New' Traditionsgeschichtliche Approach" (e.g. Recovering the Original Gospel of Thomas, Chapter 1) and it is a repeated emphasis across the two volumes that Thomas and Thomas traditions went in and out of different instantiations in oral performance and literary text. These different performances interacted with one another and flowed into one another. It is probably not fair to say, then, that she is applying form critical methods towards the goal of ascertaining literary history. She is rejecting the idea of literary history as traditionally configured, and she is attempting to rework the usual tools used for analysis.
Nevertheless, it is interesting to reflect a little further on Patterson's general point, about the potential for confusion between form-critical methods and literary history. On one level, I am encouraged by what he says because I have been banging away at a similar point in a different context for some time, that we should be careful not to confuse age of traditions and literary priority. It is a mistake that I think underpins the Q hypothesis, where signs of an older tradition are always taken as signs of literary primitivity. I have argued that Q forces the whole discussion of Christian origins onto a literary footing, with double tradition material getting projected always onto a literary text.
On the other hand, though, I wonder whether we need to avoid driving too hard a wedge between oral tradition and literary text in the thinking of the form critics. After, the form-critics often thought of the phenomena they isolated in the oral tradition as being continuous with the phenomena they could see between different literary texts. The same laws applied when they were tracking the development of a saying in the pre-Marcan tradition and when they were looking at the way that Matthew edited Mark, and so on. So the process of allegorization of parables, for example, began in the pre-Marcan oral tradition, but continued with the evangelists. The trajectories they theorized began in the pre-Gospel era and continued in the literary phase.
In the end, I think that the problems with form criticism are such that it is not particularly useful in tracking the development of the tradition, but at the same time it is worth attempting to understand how it worked in the thinking of the greats in order to work out how it still affects our thinking about Christian origins.