Ethical Nihilism
Hedonism

Ethical nihilism : per Platonist Paul Shorey, ethical nihilism is a belief system which

questions all standards of morality and aesthetics, and confuses justice and injustice, beauty and ugliness.

Prof Shorey goes on to say that

Its gospel is expressed in Mr Oppenheim's lines :

Let nothing bind you.
If it is duty, away with it.
If it is law, disobey it.
If it is opinion, go against it.
There is only one divinity, yourself,
Only one god, you.

Prof Shorey died in 1934, so presumably Mr Oppenheim was writing before then.

Interestingly, though, Ayn Rand, the self-styled "objectivist" philosopher whose embrace of atheism, egotism, money, and greed is so beloved of our 21st-century Republican Party, wrote something very similar -- in 1938 :

I am done with the monster of 'we,' the word of serfdom, of plunder, of misery, falsehood and shame. And now I see the face of god, and I raise this god over the earth, this god whom men have sought since men came into being, this god who will grant them joy and peace and pride. This god, this one word: 'I.'

~Ayn Rand, Anthem

Needless to say, Plato, who abhors private property and the greedy for gain, and who believes that Men should seek Communion with the Gods -- plural -- constantly -- doesn't agree.

But he does understand how such belief systems as Ms Rand's materialize -- and where they lead :

when a male ceases to deem worthy the principles of kalon and agathon -- that is, of moral beauty and manly goodness -- and to think that they are no longer binding on him, and cannot discover the true principles, he'll be likely to adopt a way of life which flatters his desires

-- that is to say, hedonism.

He'll put pleasure above Manhood, and make what little Manhood he has left serve that pleasure --

till he has no manhood at all, and is completely an-andros -- UN-manned.

Ethical nihilism is inextricably intertwined with:

Hedonism : per Platonist Paul Shorey, the doctrine of the unqualifed identification of the pleasurable with the Good -- as in "it's all sex and it's all good."

See also Areté.

And:

AGOGE VI: The Strife of Valour: Austerity and Equality at Sparta.