Dear Mark,
I am not sure whether it is a valid question you are asking.
But I believe it's a valid answer to your question
= the reason (that this society does not exist) is that Oscar is talking about an ideal society.
here is a definition of the word "ideal":
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Main Entry: ideal
Part of Speech: adjective 2
Definition: conceptual
Synonyms: abstract, chimerical, dreamlike, extravagant, fanciful, fictitious, high-flown, hypothetical, imaginary, impractical, intellectual, ivory-tower, mental, mercurial, notional, quixotic, theoretical, transcendent, transcendental, unattainable, unearthly, unreal, Utopian, visionary
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As Oscar said an IDEAL might be utopic yet not impossible.
If it is technically impossible then it is not a valid ideal (thinking in an ancient Greek style)
An ideal model is there to give a direction and maybe finally reaching it.
Typically, ideals are not achieved by themselves - the word implies a conscious choice to go in a certain direction.
For example one could say that democracy is based on the ideal of equal chances (that does not mean that democracy is equal chances). Democracy is not happening until somebody comes up with the abstract idea of creating a group which chooses it's own leaders who have a limited power for a limited period where every member of the group has a formally equal influence on the style in which he is being ruled by the leader/s.
One of the rare cases where an ideal is in fact a real natural state is Wai's diet. In that sense it is not an ideal but a historical discovery.
But even in that case in our modern world the diet will not happen if we don't make a choice...
G.