Many thanks to Dennis C. for this helpful list of passages from the Gospel of Thomas that are paralleled in the Synoptics.
I recommend that the reader try the experiment for any given passage:
1. Read it in Thomas.
2. Ponder why it is recorded after the previous saying, and before the next saying.
3. Look up a parallel verse from one of the Synoptics.
4. Do the same (step 2) for the parallel verse.
5. Ask yourself which was the original context for the saying: Thomas or the Synoptic?
6. Ask why it is that Elaine Pagels is a professor at Princeton, and you’re not.