Canon re:inclusion of Thomas

I've been reading with interest the recent posts about including the Gospel
of Thomas in the NT Canon.  I asked my one of my religion professors about
why the gospel of Thomas was not included in the NT Canon.  He said, and
I quote "The early church-meaning the functional church or the orthodoxy of
the first centuries looked at the writings which were available and freely
ciculating and RECOGNIZED as canonical that which stood out as CLEARLY 
authentic and reliable sources which providence working through the apostles
and their associates had written.  This providential element in their origin
and preservation made an adequate body of literature tested by CONTENT,ORIGIN,
and WIDESPREAD Christian acceptance.  cf. Josephus' description of the OT canon
emergence."  The gospel of Tomas was not widely accepted by the early Christian
church, in fact it was regarded as Gnostic.