This was a very good question made over at Facebook which deserves a crosspost. Others may have additional thoughts that would be good to preserve on this point:
DG: "...πᾶν ἀγαθὸν καὶ κακὸν ἐν αἰσθήσει..." All good things and bad things are in sense-perception... Letter to Menoeceus, 124. ... Are intellectual pleasures found in sense-perception? Are there any good or bad things (pleasure and pain) not found in sense-perception? Where do pleasant memories or dread of future events factor in with respect to sense-perception?
I think the general answer to your question is that pleasure and pain itself, as a faculty of feeling, is categorized as within the Epicurean canon of truth, and it weighs in, as a feeling, on all experiences, physical and mental, that come to our attention. So presuming you mean "found" in the sense of "included" I think the answer to the first question is "yes" and that is an extremely important point, and I would include everything we think of emotions/feelings/thoughts/bodily sensations --- everything that comes to our attention -- within the broadest definition of things that we sense and feel pleasure or pain in.
As to the second question there is an ambiguity in the definition of "sense-perception" and it can be argued that Epicurus seems to generally refer to everything that comes to our attention or consciousness as sense-perception. Consider these: PD02. "Death is nothing to us, for that which is dissolved is without sensation; and that which lacks sensation is nothing to us." So there is nothing intrinsically good or bad in itself that is not within that wider sense of the word sensation. Also, from Torquatus in On Ends: "Hence Epicurus refuses to admit any necessity for argument or discussion to prove that pleasure is desirable and pain to be avoided. These facts, be thinks, are perceived by the senses, as that fire is hot, snow white, honey sweet, none of which things need be proved by elaborate argument: it is enough merely to draw attention to them. (For there is a difference, he holds, between formal syllogistic proof of a thing and a mere notice or reminder: the former is the method for discovering abstruse and recondite truths, the latter for indicating facts that are obvious and evident.) Strip mankind of sensation, and nothing remains; it follows that Nature herself is the judge of that which is in accordance with or contrary to nature. What does Nature perceive or what does she judge of, beside pleasure and pain, to guide her actions of desire and of avoidance? "
As to the third question I would say that memories and thoughts come to our attention in way analogous to seeing or hearing things, and so pleasure and pain weigh in on those just like they evaluate everything else of which we are conscious.
DG: Cassius Amicus thank you very much for this well thought out response! ... I'd like to investigate this claim further: "...and it can be argued that Epicurus seems to generally refer to everything that comes to our attention or consciousness as sense-perception." I also think that you have given me enough here to understand the lines Epicurus might take to respond to my questions. Best,
All this is no doubt a difficult subject and I certainly admit the possibility that I am wrong - just giving you the best analysis my limited mind can muster after some years of study. I've constantly run into the issue that the three legs of the canon (including pleasure/pain and anticipations) seem to be understandable only in terms of them being considered by Epicurus to be kinds of "faculties" in themselves - each being independent channels or connections with the outside world. There is of course much controversy over whether anticipations should be labeled in that way, and it's not altogether clear that feeling (pleasure and pain) is that way either. But if Epicurus was considering them to be co-equal "standards of truth" that were not influenced by opinion (and thus subject to error) but as faculties that should be accepted at face value (subject only to correct by later observations from the same source) then I think you do have to consider them as "faculties."
There are big questions as to whether "everything" has to come originally through the five senses, or whether pleasure/pain and anticipations are disposed in certain directions at birth. I take the position with DeWitt that Epicurus thought it was important to see those two as being at birth subject to some degree of "programming" or "disposition" but yet requiring stimulation from the five senses to be "activated." Apparently later Epicureans after Epicurus diverged from Epicurus on this point, and there again I agree with DeWitt's contention that they made a grave mistake in doing so.