Nihilism is where fulfilled desire becomes the sole aim of freedom.
Freedom is understood more and more in the abstract, nowadays, rather than in the concrete. The modern understanding of freedom means getting whatever you want - whatever you can imagine - even when what you want is a logical contradiction or an inherent impossibility... and where there are barriers or restrictions - any conditions at all impinging on your desires - they must be removed. Freedom is seen not as the ability to use what you have to accomplish all you can, but as simply the absence of restrictions of any kind, be they physical, moral, legal, or what have you.
A common, natural, sane individual will understand and accept that he is free in many ways, but not nearly in all. A free and sane man may step out of his door and run in any direction he likes, but he is not free to run like a horse, because he does not have the body of a horse. In trying to run like a horse he will find that he is no longer able to run even as a man, and is really no closer to running like a horse.
But the modern mind will see the man's ability to run in only one, limited way (that is, as a man) as a defeat and even an injustice. Freedom is practically worshiped as an abstract ideal, rather than being understood and welcomed as a real, vast panoply of concrete possibilities.
This is where the modern world turns everything on its head. The human body - that marvelous and mysterious engine of all our earthly freedom - has been perceived more and more in modern times as a hindrance and a restriction... almost like a cage of flesh. Whereas a sane man will give thanks for the gift of two working legs, an insane man will find it absolutely intolerable that he is not allowed instead to have fins or wings or a hundred legs like a centipede.
And so, we have for years heard of those unfortunate individuals who insist that they are really women trapped in the bodies of men, or men trapped in the bodies of women. This has passed, in my lifetime, from being seen as a disorder and a mental sickness (in need of treatment) to being simply another desire in need of fulfillment. Transsexuals are even legally recognized by most states as being whichever gender they choose for themselves, even going so far as to change their birth certificates.
"Oh, but how these people suffer", you might say... "they really find life intolerable until they can be set free by means of surgery and hormone treatments. They only need our acceptance and understanding".
Let's say that's correct. Let's say that a person's internal vision of themselves - their interior life and imagination, their desires - is what really makes them who they are, and that accidents of birth should not be seen as absolute, should not prevent them from pursuing their dream of happiness in whatever way they see fit.
In that case, one will need to give the same consideration to those who are said to have Body Integrity Identity Disorder... that is, those who feel they are amputees trapped in healthy and (intolerably) whole bodies. Inside, you see, they just know they were meant to have only one arm, or no legs. Oh, how they suffer (this I don't doubt). There are now more doctors (still only a few, but a growing number) willing to consider granting these people what they desire. By what modern, material philosophy can they be denied?
And then, there is the Cat Man. Formerly Dennis Avner, Cat Man (now his legal name) has spent countless hours and great amounts of money and says he has "transformed (him)self into a tiger". On what grounds, pray, would a proponent of legal transsexualism deny that the former Mr. Avner may really be a cat trapped in a human body? On what grounds would they argue the point? After all, only he can know how he really feels inside, which is all that matters. And that being the case, what cold-hearted prig would (should Cat Man ever desire it) deny him the bliss of mating with or legally "marrying" another tiger... one of his own kind? Why shouldn't he be happy on his own terms, as gay "married" couples wish to be happy on their own terms?
A healthy man who wishes to amputate his own limbs is demonstrably insane (at least on that point), and any worldview that maintains otherwise is equally insane. We do the deluded patient no service at all when we confirm him in his delusion - when, instead of working to draw him out of his nightmare, we enter into his nightmare with him... or else we uncork his nightmare and loose it on the whole world.
We all want understanding and acceptance, but to understand and accept insanity as anything but insanity is ruinous, is cultural suicide. We are already headed down that road. The question is, are we too far down to turn back?