> Could you say that nihilism is rejecting values imposed upon the individual, while hedonism is asserting the right to arbitrary pleasure?
I'm going to answer your question and, in doing so, answer another comment that argued with me about the definition of nihilism.
The short answer to your question is "no."
According to Wikipedia (https://en.wikipedia.org/wiki/Nihilism):
> Nihilism is a family of views within philosophy that rejects generally accepted or fundamental aspects of human existence, such as knowledge, morality, or meaning.
> There have been different nihilist positions, including that human values are baseless, that life is meaningless, that knowledge is impossible, or that some set of entities does not exist or is meaningless or pointless.
If existence doesn't exist, then there no values because nothing exists. If morality does not exist (or is baseless), this is a rejection of values since morality is a code of values. If knowledge doesn't exist or is impossible, this is a rejection of values since values are that which we seek to acquire and keep, and so if you can't know anything then values become meaningless because you don't know what you value or what you ought to value. If nihilism is a rejection of meaning qua meaning, then you are rejecting values since nothing can mean anything, and therefore values have no bearing on your life or existence since life and existence itself is meaningless (no matter how you define "meaning").
Therefore, nihilism is the rejection of ALL values regardless of whether they are personally chosen values or "imposed" values.
There may be degrees of nihilism. Some nihilists may reject certain values while choosing to retain others. But no matter how you slice it, nihilism is a declaration of war on values themselves.
Now, slight digression: my personal opinion is that on a fundamental level, all values must be chosen by the individual since only individuals are capable of forming value judgements. Groups can agree upon values, or say "if you want to belong to this group then you must accept certain values ('our' values)", but at the end of the day the individual must ultimately decide what values to adopt.
Hedonism broadly refers to a philosophy of "whim worship" or "pleasure seeking." It values pleasure for pleasure's sake and considers anything that brings pleasure to be "good" and anything that does not to be either "bad" or "neutral."
While hedonism may very well assert the "right" to "arbitrary pleasure", I disagree that that is its defining characteristic, since you can assert that right while also acknowledging that pleasure seeking for pleasure sake can be self-destructive and therefore morally wrong (ex: bank robbing and heroin abuse).
[Edit: upon re-reading the above paragraph, I think a better example here is to focus on drug abuse. I personally think that you have a "right" to put whatever you want into your body. And abusing hard drugs might feel good and bring you lots of immediate pleasure. That doesn't mean that it is "good for you" and therefore, under my code of ethics, self-destruction via drug abuse or other is immoral. But I'm also trying to steer clear of discussing the definition of morality, and why human beings need morality, because that would quickly get off topic].
I would say that pleasure is a positive value (vs the negation of values), whether you are a hedonist or not, and therefore hedonism and nihilism are mutually exclusive by definition. Though I would also argue that both are destructive since one dispenses with values all together while the other uses pleasure as a SOLE determiner of what to value and therefore values that which can be destructive.