And even
that is something that is not unchallenged. The idea that Thomas already existed in the 1st century in the form(s) that we have it today is, in reality, in the very small minority. At best, what people - even many of those in the so-called ‘early’ camp - think that the ‘core’ material (a portion out of the 114 sayings attributed to Jesus recorded in there) of that gospel may have already been in circulation during this time or before, but many think that Thomas as a literary work did not come into existence until much later.
All in all, we only know of at least nine gospels which were composed before AD 175, and one of these (the Protoevangelium of James) does not, strictly speaking belong to the ‘gospel’ genre at all. Excepting the Protoevangelium of James, these other eight gospels are (based on
William Petersen’s list):
Gospel of the Ebionites (c. 125?)
Gospel of the Egyptians (c. 125?)
Gospel of the Hebrews (c. 125?)
Gospel of the Nazoraeans (c. 125?)
Gospel of Thomas (c. 140?)
Gospel of Peter (c. 150?)
The ‘Egerton Gospel’ (c. 150?)
Gospel of Judas (c. 170?)
And even then, the dates Petersen gives for the canonical gospels (which are fairly standard in academia today, although some competent people would push for earlier dates) acknowledge them to the earliest
known gospels, an idea which is shared by the vast majority.
Mark (c. 70?)
Matthew (c. 85?)
Luke (c. 90?)
John (c. 100?)