https://suttacentral.net/kv18.8/en/aung ... ight=falseControverted Point: That one who has attained Jhāna hears sound.
Theravādin: If so, it must be equally allowed that he can also see, smell, taste and touch objects. This you deny … You must also allow that he enters Jhāna enjoying auditory consciousness. You deny, for you agree that concentration arises in one who is enjoying mental objects as such? But if you admit that anyone who is actually enjoying sounds hears sounds, and that concentration is the property of one who is actually enjoying mental objects as such, you should not affirm that one in the concentration of Jhāna hears sounds. If you insist that he does, you have here two parallel mental procedures going on at the same time … .
Pubbaseliya: But was it not said by the Exalted One that
“Sound is a thorn for First Jhāna”?
Hence one in Jhāna can surely hear sound.
Theravādin: You say that one in Jhāna can hear sound, and quote the Word as to it being for First Jhāna a “thorn”. Now it was further said that thought applied and sustained is a thorn for Second Jhāna—does one in Second Jhāna have applied and sustained thought? … Again, it was further said that the mental factor last eliminated is a thorn for the stage newly attained—zest for Third, respiration for Fourth Jhāna, perception of visible objects for consciousness of space-infinity, this perception for that of consciousness as infinite, this perception for that of nothingness, perception and feeling for cessation of these in trance. Now is “the thorn” actually present on the winning of the stage whence it is pronounced to be a thorn? If not, then how can you say that the “thorn” of hearing sound is present to one in First Jhāna?
I think this is a mis-reading. What tends not to be noticed is that the Pubbaseliya are said to agree that seeing, smelling, tasting and touch do not occur whilst in Jhāna (i've highlighted this above). The Pubbaseliyas then weren't arguing that the 5 senses occur in Jhāna, but were rather arguing that in order for sound to disturb the meditation it must be the case that whilst in Jhāna it's possible to hear sounds. This centres around a wider debate, regarding how someone can be pulled from the 1st Jhāna by hearing. To some, it happens when the Jhāna is "weak". To others, like the Pubbaseliya, the 5 senses are shut off whilst in Jhāna but even there its possible for it to be disturbed by sound. The point however is that even for this branch of the Mahāsāṃghika, Jhāna was thought of as being a state where the 5 senses are temporarily abandoned. That view isn't being debated. What is being debated is how a distraction can occur whilst in Jhāna. They actually have a similar view to Theravāda regarding what Jhāna is like:
You deny, for you agree that concentration arises in one who is enjoying mental objects as such?