* Warning: If you have a blind faith in Esperantism (and aren't open to different ideas), you may find this blog entry offending.
Finally I feel prepared both intellectually and emotionally to articulate why I became convinced that a "universal" language is insufficent to unify the mankind and there is a far better solution for this purpose. Nevertheless, this attempt is a rather paradoxical one as I'm going to explain the limitations of language with a language.
Esperanto must be the most widely known and used "universal" language. The greatest obstacle Esperantism faces as the movement to use Esperanto to unify the mankind is ironically Esperanto itself, or a blind faith that a "universal" language is sufficient for this purpose. But the truth is that no problem can be solved with the same level of consciousness as Albert Einstein said.
Zamenhof was rather naive in this respect. I'm not sure how many Esperantists are aware that one of the most important functions of language or any specific language is to articulate or divide the world, including all the creatures inhabiting it. Language is a tool of duality and its illusions. Esperanto is no exception to this. So Esperantism has to trascend its reliance on Esperanto or any other language, whether "universal" or not, to attain its purported goal.
There is no doubt that the level of consciousness of average Esperantists is higher than that of their conpatriots in their respective countries of residence. But as long as they are stuck in language, they are also stuck with the illusions and limitations of duality, which in turn prevents them from raising their level of consciousness.
Another important problem neither Zamenhof nor many Esperantists seem to be aware of is that a language is a powerful tool to forge, maintain and strengthen the collective ego of the social collective it serves, and Esperanto is no exception to this, either.
When I told one prominent Esperantist that I had completely stopped my involvement with Esperanto, he called me a "traitor". But I didn't "discrimiate" Esperanto; I've completely stopped my involvement with all the other linguistic ideologies/movements that used to occupy me for decates, most notably Yiddishism, which in my opinion, is far more illusionary and reflects a much lower level of consciousness of its supporters.
This may sound unbelievable and unacceptable, but we human beings are already unified. We are sparks of the only presence there is, which is known in various terms such as G-d, Universe, etc. We are like waves of one and the same ocean. To claim that each wave has a separate existence is nothing but an illusion. So is the case with us human beings. This illusion created by our egoic mind, which in turn is maintained mainly by language as its gatekeeper.
So all we have to do is just recall that we are "waves" of Oneness. No "universal" language alone can help us attain this goal because of its very dualistic nature. The best way to raise the level of consciousness I've found so far is to study teachings of nonduality intellectually and practice them through direct experiences without any language, thus bypassing the dualistic illusions and limitations it creates.
The most sophisticated Jewish version of nonduality I've discovered so far is Chabad Chassidus, and this is why I've become so enthusiastic about its teachings and practices. It's true that it does use human languages, but words uttered by nondual masters such as Chabad rebbes can transcend the illusions and limitations of the egoic mind.