he best way to discuss pleasure, pain and neutral is by leading with the sensations and feelings, not by leading with logic.
Godfrey I agree that is the *best* way, and I think that is what Torquatus is reporting was insisted on by Epicurus himself in stating that no more proof is necessary or appropriate than pointing to animals and pleasure and snow and the like.
But it's not the **only** and as Torquatus said it appears the later Epicureans (and I think Epicurus himself too) decided that for multiple reasons we cannot abandon the field of logic and philosophy itself to the pin-head Platonists. So if we are going to argue for pleasure on philosophic grounds, we have to have rigorous and bullet-proof logical statement of how all this fits together.
Were Emily Austin to say "I think Epicurus was right -- look at what babies do! - I rest my case" and close her book and sit down for the rest of the semester, she would likely be in very hot water, and probably not satisfied with herself either.
So I don't think there is really an tension here -- for those who will accept the direct physical example that you mentioned, that is all that is needed.
But are those people really going to be secure in their confidence that they are correct if they pick up literally ANY book or article written by anyone whose last name is not DeWitt or Austin and read what they have to say about Epicurus?
Unfortunately I am afraid the answer is clear and we have to BOTH attack on common-sense observation, and on on logical philosophic grounds, just like the ancient epicureans did.
I was thinking just a minute ago something related to this; In Philebus, Plato has Philebus stab his argument in the heart by admiring that pleasure has no limit. In On Ends, Cicero cannot bring himself (probably on pain of an Epicurean uprising) to put words in Torquatus' mouth that undermine his own case. Torquatus never deviates from the Epicurean formula, and all of his statements are textbook Epicurean correctness. But what Cicero does NOT do is allow Torquatus to give a full explanation of Epicurus' reasoning that goes into detail about how Epicurus reached these conclusions.
We can do that today, by mining Lucretius and the rest of the texts and interpolating between the lines what was really going on in Epicurus' argument.