I will throw out there, though, that although pleasure is felt at all normal times as a response to a specific experience (as is pain), I think the activity itself is not the pleasure or the pain.
Yes I agree that is an important distinction. The pleasure is the total contextual experience as the same activity can generate pleasure or pain in different contexts.
On absence of pain/fullness of pleasure, I am baffled by your answer-- it seems like you are disagreeing with the synonymous aspect, although you say you aren't, and I can't get a grasp on your train of thought.
I "think" our issue here is this - I am constantly switching contexts between Epicurus making the statement "maximum pleasure is absence of pain" to a student in Athens vs. the same statement being made at a philosophy department class in the world of 2019.
I am thinking that because the Athenian student would have had full access to Epicurus' views and an understanding that "there are only two feelings" and that Epicurus was campaigning in favor of pleasure as ordinarily understood, the Athenian student would never be confused. The Athenian student would know that "we would never know the good without ..." the normal pleasures of action, so he would never consider divorcing the term "pleasure" from "normal active pleasures.
I do not believe that the statement "maximum pleasure is absence of pain" has the same contextual meaning to a 2019 philosophy student. Due to many different factors, 2019 students will most frequently infer that "absence of pain" is a reference to some kind of esoteric/mysterious state intended to mean something similar to nirvana or sensory deprivation or just simple stoic emotionlessness. As a result, I think someone today who says "the highest pleasure is the absence of pain" is probably intending his hearer to understand something very dissimilar, or even the opposite, of what Menoeceus (or any other Athenian of Epicurus' age) would understand.
I see this is very similar to "death is nothing to us." These words in 2019 in English imply flippancy; imply almost a nihilistic message that "LIFE is not important to us." I don't think that the same message would have been heard by an Epicurean Athenian of 200 BC. I think the message was "being dead is a state of nothingness - being dead is being reduced to nothing" due to the absence of sensation. Rather than a message of flippancy I think it is conveying that we have no concerns after we are dead because there is no sensation that would drive a concern. And one of the most important results of "death is nothing to us" properly understand is something very close to "life is everything to us." As I remember DeWitt saying somewhere, pain and pleasure "have meaning only to the living."
Does that explanation help bridge our issue, or make my viewpoint more confusing?
On the size of the cup... I guess this is just me seeing the metaphor differently. I don't see the cup as representing numbers of experiences but the organism's feeling capacity. I don't think it helps to imagine people's cups of different sizes, if the cup represents feelings.
On this issue I am attempting to consider a concern that will present itself to many people to the effect that "it isn't fair" that everyone doesn't have the same size vessel of pleasure. I think this will manifest itself in many ways but maybe most obviously in comparing the life of a person who dies in childhood vs one who dies at 90 years old. Are not the feelings experienced by the 90 year old in some way larger in quantity than those of the child?
I am also concerned about the question I raised as to how we would know that the choice of living in the cave would not produce "the best life" for a human being. The minimalists will argue that by keeping the total experiences small in number, there are fewer pains, and if the pains go to zero we should acknowledge (given our formula) that this is the best life possible. Such a person might be from a background where he or she never thinks about coming out of the cave.
I do see issues in thinking about the vessel being changeable in size, so I want to think about that more, but I suspect I am going to think it best to deal with that issue as a limitation in the model, and a contextual issue, because the "person living in a cave on bread and water" is so dominant a theme in Epicurean academic commentary that I think we almost immediately have to deal with that situation using the vessel analogy in some way. And it might be useful to relate the "size of the vessel" to the part of life that is within our agency / "free will" to influence.