As far as reacting to the religious or spiritual content of the Gospel of Thomas, I have never personally been as drawn to it as I have (for example) the Sermon on the Mount, or the Johannine tradition. Although I think something like half of the sayings are at least quite close to sayings found also in the canonical gospels. I don't personally have any objection to the Gospel of Thomas, content-wise. The things that I find worthwhile about contemplating it as an early Christian text are:
- As evidence of the fluid, varied, and chaotic nature of the growth of early Christian belief, and what that has to say about "biblical authority", or defining what is and is not "Christian" teaching. Discussions about these various streams of thought (c.f.
the OYC intro to the N.T. course) should change how Christians think about Christian dogmatics, in a helpful and less fundamentalist way. For example in the Open Yale lectures there are comparisons made between the pastoral Pauline epistles and the viewpoint of the gospel of Paul and Thecla, or between the viewpoint of the gospel authors. The Gospel of Thomas fits into the same point. It's a point that I think a lot of modern Christians need to become more aware of.
- As evidence against an excessively literalistic hermeneutic of Christian sacred texts, and as a reminder that the mode of reading texts as "histories" in a modern sense doesn't necessarily best reflect traditional readings. The Gospel of Thomas makes no attempt at giving a history, it's a collection of sayings that are obviously expected to be read in a more nuanced and symbolic way. The authors obviously intend a more "spiritualized" reading. Again I think this is a point that Christians need to hear more and take into account in their approach to Christian tradition and the Bible.
Selection criteria, reasonable or not, are still arbitrary and subjective.
I think that any appreciation for the history of Christianity as a religion makes clear that any idea of the canon of the Christian Bible as something divinely established is untenable, and if, for the canon to be "non-arbitrary" or "objective" requires an absolute ground, then clearly that can't be established. However, to me, the word "arbitrary" has this connotation of something being chosen on a whim, or without consideration, and I don't think that's an entirely fair assessment of the history either. I think it's undeniable that the formation of the canon was enacted following the (subjective) opinions of very human Christians, and especially church leaders in the 4th century. To the best of my knowledge though, their decisions seem to reflect both a consideration for what texts were already widely in use and valued among the Christian churches, as well as some attempts at "objective" criteria, even though those criteria were obviously also evaluated subjectively. The primary criteria expressed by church leaders was basically the idea of apostolic authority. Texts thought to have been authored by apostles or by close disciples of the apostles were favored.
Of course the irony is we now know that their evaluation of authorship was almost certainly wrong in most cases, which is yet another point to be added about why Christians shouldn't be too dogmatic about the nature of canon, but I think sometimes views of the formation of the Bible take on this gloss wherein Constantine is the primary villain, and the leaders of the churches acted solely out of some political machination or other, and that doesn't seem like a reasonable portrayal of events either. Mostly I think the dichotomy arises from presuppositions about the nature of biblical authority that overly fundamentalistic, where either the text is dictated and established from on High, or else it is entirely arbitrary, subjective, and (as some will infer, although this is not necessarily your implication) valueless. Rather, when I read the writings of ancient Christian theologians concerned with the nature of scripture and its interpretation, i see mostly a more pragmatic concern. They favored texts that they felt were spiritually richer, but also they valued the tradition that asserted apostolic authority for those texts and the collective opinion of the churches. But the seat of authority (and not necessarily an absolute authority) for them was the church itself, as a living tradition, rather than it being a question of tricking everyone into thinking that one specific collection of texts was divinely ordained as the one and only true Bible.
Anyway, to me, what I hope is that these considerations lead Christians towards a self-understanding that is less based on absolutizing a doctrinal orthodoxy in a fundamentalist way, where everyone else is a heretic, and more towards a self-understanding that accepts with humility the provisionality and humanness of all of our knowledge, or the value of texts, or the authority of institutions, but sees a Christian life as more a matter of seeking to express our lives in a Christ-like way, in love, gentleness, forgiveness, and etc. All the elements of Christian life which are symbolized by the "Spirit" in the N.T. texts, which gives life, while the "letter" gives death, so to speak. The historical realities about the formation of the canon, or an awareness of the wide breadth of "Christian" belief throughout history, should point towards the fact that certain views about doctrinal orthodoxy are impossible to sustain.