In the city where I live (San Francisco) one can hear dozens of languages spoken on the streets other than English. If you are just overhearing conversations, it doesn’t matter. But often I have to try to understand other people who have a limited grasp of English or who have a heavy accent. Even my SO, who has been in the U.S. for 40+ years, has not improved in either understanding nor pronunciation of English in the 22 years we have been together.
In Ursula LeGuin’s novel “The Lathe of Heaven”, at one point everyone is turned a sort of uniform grey color, in order to remove racism from the world.(I don’t think it worked, there was some unintended consequence that I don’t remember.).
What would be the unintended negative consequence if suddenly, overnight, the world changed so that everyone had always spoken the same dialect of the same language? I don’t care what language (it needs to be a modern, fully realized language, however), just that we all wrote, spoke and could understand the same tongue.
The benefits would, I think, be obvious - better understanding between all people. Even cultural differences would be minimized, since language is so strongly tied to culture.
One big negative consequence I can think of is the loss of cultural richness as represented by different languages, their literature, and the different ways they express the human experience. Are there others? Would the benefit be worth the price?
Roddy