According to Greek Hedonists, Epicurus, and the modern school of Utilitarism pleasure is the only instrinsic good. It seems that this philosophical doctrine is simply the axiological postulate that pleasure is the good. I do not think it is connected to "good" in terms of ethics and morality but perhaps epistemology or even aesthetics. The first [epistemology] may see good in knowledge (Epicurus et al.); this knowledge is good, and it is a pleasure to have it; and the second [aesthetics] in music or art (Schopenhauer says that music represents the whole will).

However, Plato seemed to have already succinctly refuted the theory in The Republic. According to Plato, those who say that knowledge is the good, they must admit that the knowledge that is good must be knowledge of the good. And then Plato states:

Well, are those who define the good as pleasure infected with any less confusion of thought than the others? Or are not they in like manner compelled to admit that there are bad pleasures [ἡδονὰς εἶναι κακάς, hēdonàs eînai kakás, i.e. admit "pleasures to be bad"]? — Plato VI, Republic II, Book VI, 505c, translated by Paul Shorey, Loeb Classical Library, Harvard U. Press, 1935, 1970, pp.88-89)

I think I understand what Plato meant. If there are bad pleasures, this means that the concepts of "good," "bad," and "pleasure" vary independently. What I consider a good pleasure, such as listening to opera, may be insufferable to you. According to this, pleasure seems to be a purely subjective concept.

Nonetheless, I have some questions that I would like to share and debate with you:

What are the bad pleasures according to Plato? Does this really depend on each of us and how we understand Hedonism?

Are there objective pleasures? Can these be drawn from the boundaries of good and bad?

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Recommended readings:

Polynomic Theory of Value, Pleasure and Virtues by Kelley Ross.

Plato - The Republic. Book VI.