The 'orthodox' position taken by many scholars, for example Stephen Patterson, is that the Gospel of Thomas represents early oral traditions predating the Synoptic gospels and separate from their sources. But do the arguments denying any dependency of Thomas on the Synoptics, and therefore a later date, really hold water? Mark Goodacre skilfully demolishes many of these claims, often with a dry wit. So the case that, as per Patterson, Thomas cannot be dependent on Matthew because otherwise he would use characteristic Matthean phrases more often is shot down by Goodacre, noting that if someone copied a section from Patterson using his characteristic phrase "gnosticising proclivities", but a judge threw out a plagiarism charge by Patterson on the basis that the rest of the plagiarist's work does *not* include that phrase, "it is doubtful that Patterson would be convinced".
Demonstrating that arguments against dependency on the Synoptics are invalid is one thing, but showing actual dependency is another. Fortunately Goodacre has arguments up his sleeve on this too, for example the "missing middle". Many of the parables as related in Thomas have the beginning and end, but not the middle part. We from our position of complete familiarity with the Synoptic parables simply do not notice this and supply the rest of the story ourselves so they are immediately understood, but taken in complete isolation the parables of Thomas are frequently incomprehensible. Goodacre argues therefore for dependency.
Goodacre argues that the author of Thomas, writing in the 2nd century, incorporated Synoptic material to lend authority to his own material. A similar argument, though arguing for dependency on the Diatessaron, has been put forward by Nicholas Perrin - see Thomas: The Other Gospel.
This is a thoroughly well written and argued work demonstrating the fallacy of many of the arguments put forward for no dependency, whilst also presenting possible evidence in favour of a real dependency. Some familiarity with the Koine of the Synoptics for when the author compares with the Oxyrhynchus fragments of Thomas (and perhaps indeed some familiarity with the Coptic of the Nag Hammadi Codex II text of Thomas too) is useful but certainly not essential.