Esperanto was diligently designed by a multilingual professional with a clear purpose in mind: To distill a language which would retain all communicative functions found in other languages, with a minimum of idiosyncratic complications.
Why? Because a lot of what makes us human is that we can communicate with each other, and so inability to communicate with most humans is an obstacle to full recognition of their their humanity.
Obviously it isn’t the only obstacle but it is a significant one, and soluble.So Zamenhof dedicated his life to solving it successfully.
The language has been learned and used by millions of people for over a century, and has adapted as well as English to the advent of the computer age, so it would be fair to say that it has passed the test of time.
Today, we have even more reason to appreciate that high quality human life on this planet in the next few generations is going to require global citizenship.
Natives clearing forest in Brazil matter to us, multinational corporations doing similar things worldwide matter to us too, to all of us.
Most people in the World do not speak English, and will not speak English in their lifetimes. They do not have the time, or the money, or the access to teachers to make it happen.
So, we can leave them out... or meet them halfway. How would you like to be treated if the shoe were on the other foot?
Just as a handshake involves both parties stepping forward and extending a hand, so learning Esperanto takes both parties (adults) about 10 hours of instruction and 100-200 hours of practice.
Esperanto, as a “linguistic handshake”, is more affordable to both parties than the 600-2200 hours that natural languages require to reach the same fluency.
Besides being a beautiful example of decent behaviour, win-win “green hat” thinking and all sorts of other wholesome attitudes and values that you would want your students to absorb, Esperanto offers them a wide variety of immediate and lasting advantages. But that's tomorrow's post :-)