SOCRATES: I omit ten thousand other things, such as beauty and health and strength, and the many beauties and high perfections of the soul: O my beautiful Philebus, the goddess, methinks, seeing the universal wantonness and wickedness of all things, and that there was in them no limit to pleasures and self-indulgence, devised the limit of law and order, whereby, as you say, Philebus, she torments, or as I maintain, delivers the soul. — What think you, Protarchus? …
I admit I need to read Philebus in full, but, just riffing on the above excerpts + Seneca, it seems to meet that Plato (via "Socrates") is conflating (on purpose) pleasure and desire. The *desire* for pleasure is infinite; and the things (mental and physical) from which we can derive pleasure are probably innumerable. But pleasure, as a feeling, is limited to the point where there is no pain, when the body is satiated. Full satisfaction is the limit of pleasure. I think Epicurus had that absolutely correct. The other philosophers took for granted (from *their* perspective!) that pleasure was bad, base, inferior and then designed their philosophy around that "a priori knowledge." Epicurus started from the ground up to investigate where pleasure came from, and decided it was nature's natural "stop and go" signals, then began to philosophize how we interact with pleasure.