What kind of gospel is Thomas?
Thomas is usually described as a sayings gospel. Most entries begin with a short attribution to Jesus and continue with a saying, parable or brief exchange. There is no continuous birth, ministry, trial, crucifixion or resurrection narrative. That literary form is the first thing a reader should understand: Thomas is not a lost fifth version of the same story told by Matthew, Mark, Luke and John.
What manuscript actually survives?
The fullest witness is the Coptic Gospel of Thomas copied in Nag Hammadi Codex II. The codex was found near Nag Hammadi in Egypt in 1945 and contains Thomas as its second tractate. The surviving Coptic copy is much later than the debated date of composition, so the manuscript date and the date of the work must not be treated as the same thing.
What are the Greek fragments?
Fragments catalogued as P.Oxy. 1, P.Oxy. 654 and P.Oxy. 655 preserve Greek portions that correspond to sayings found in the Coptic work. They demonstrate that forms of Thomas material circulated in Greek before the surviving Coptic codex was copied. Differences between the fragments and the Coptic wording also warn against imagining one perfectly unchanged text.
Why is the date disputed?
Scholars disagree about whether some sayings preserve early independent traditions, whether the collection depends on the canonical gospels, and whether it developed in stages. Codex ISO therefore does not assign Thomas one certain date or present every saying as equally early. The evidence supports discussion, not certainty.