Day two  On the issue that a universal language is impossible.
Theoretically, a universal language is, seemingly, possible. If one day, all nations are united into one government, then, a universal language becomes possible. Yet, for this to happen, it is probably practically impossible. That is, some practical impossibilities can be a killer for the theoretical law of existence (theoretical possible). Some of critiques which I listed under "practical impossible" are very good questions, and they will be answered in detail one at a time. Before that, I will see them to be a true practical impossible but to be not a killer impossible which kills the theoretical possible.
In fact, this issue can be worked out with mathematics. Yet, it will go beyond some readers. So, let's look at some historical attempts on constructing a universal language and to see that how their fortunes were. There are, at least, having two schools trying to construct a universal language in the modern time (after Renaissance).
 The formal language school  There are many versions about this history. The widely accepted version is that Gottfried Leibniz (a great mathematician) was the founder of this school. The basic premise of this school is that the "algebra" is capable of expressing all conceptual thought, and the algebra symbolic manipulation can build a set vocabulary of human thought. In the following 400 years, many great mathematicians and linguists worked on this project, such as, Rene Descartes, Bertrand Russell, Alfred North Whitehead, and thousands of great mathematicians and linguists in the early of the 20th century. By 1950s, the entire framework of the formal language was completed. The necessary and the sufficient conditions for a data set to be a "language" were well understood. With the introduction of computer in the early 1920s, many computer languages were constructed, and all of them are subset of those formal languages. That is, the formal language was very successful and reached a towering height that mankind have never seen before. Yet, the formal language failed its original goal, to construct a set of symbolic vocabulary (100% axiomatized) to replace the natural human language vocabulary (arbitrary and chaotic) and to become a true universal language. Today, the formal language itself is universal but is not a universal human language.

 As a second language, it is 10 times easier to learn than any natural language as a second language.
 By learning Esperanto first, a person can learn a natural language as a second language much easier than a person who did not learn the Esperanto can.
 f the two claims are facts, then Esperanto is, indeed, a universal language, regardless of its small number of speakers in relation to the world population after 140 years. In 1920s, Esperanto had a chance to become a very powerful language when many Chinese linguists advocated to use Esperanto to replace the chaotic Chinese character system. If that effort were successful, there would have had over 1.3 billion people (more than 1/5 of the world population) in the world speaking Esperanto. By 1958, instead of adapting the Esperanto as the nation's language, Chinese government chose the option of simplifying the original characters to reduce the chaotic nature of the Chinese word system. Although I did not know the true reason of why the effort of Esperanto in China failed, I suspect that the possible reason is that its two claims above (a and b) are more of claims, not facts. Yet, these two claims (a & b) become the defining criteria for any language which wants to be a universal language.
In 1980s, the idea of a universal language came into my head. After studied the two schools above in detail, I concluded that a true universal language, if ever possible, must meet three criteria below.
 Instead of trying to replace the vocabulary of natural languages with a constructed vocabulary set as the formal language school tried, the true universal language must possess the ability and the capacity to unify and to encompass all vocabulary sets of all natural languages.
 As a second language, it must be 10 times or more easier to learn than any natural language as a second language.
 By learning it first, a person can learn a natural language as a second language much easier than a person who did not learn that universal language first.
If a language cannot meet the three criteria above, it is not a universal language. If no language (past, current or in the future) can meet the criterion i theoretically, then a universal language is theoretically impossible. Now, the issue of whether a universal language is theoretically possible becomes an analyzable issue, no need for any emotional statement anymore.
In order to answer all your critiques, I must discuss not only the issue itself but the journey which I took for resolving it. Although this is not the place for a personal vitae, knowing some of my background is useful for understanding the points of view of mine. In this Google age, anyone's background can be easily checked. "Tienzen (JehTween) Gong" is my real name, and many of your critiques are answered on some web pages, and you can find them if you Google my name. At any rate, I am listing two links below for your convenience.
 Stanford University, High Energy Physics (HEP) data base
 http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=a+Gong,+Jeh+Tween
 In WorldCat Library website
 http://www.worldcatlibraries.org/wcpa/top3mset/a8b649a71d8567aca19afeb4da09e526.html
Signature PreBabel is the true universal language, it is available at