We didn’t say that that both influences shouldn’t or “can’t co-exist” as you put it, and that isn’t what we meant, nor was it intended to…
You’re referring to the sentence: “It’s unfortunate that third-wave therapists turned predominantly to Buddhism as an inspiration for introducing mindfulness to CBT when similar ideas were already there in Stoicism.” I think you’ve misread that, with respect.
We didn’t say that that both influences shouldn’t or “can’t co-exist” as you put it, and that isn’t what we meant, nor was it intended to be pejorative regarding Buddhism. All we said was that it was unfortunate that researchers turned *predominantly* to Buddhism, when they should also have looked at Stoicism insofar as it was already an existing influence. What we meant was that both influences could and should co-exist within CBT.