"Who ever thought it good for the world to speak one language?" This means that you personally think that one language for everyone is a bad idea. This is a rhetorical question, so no point in responding. "Have you ever thought that it may be good for the world to speak one language?" This may be what you really mean, to open up a discussion. I'll answer this one. Basically, no. As an English speaker, I realise it's impossible because local influences will always affect how one speaks the language. The influences are basically political, geographical and cultural. If a single language were agreed upon, it would take merely a handful of years before you started seeing mutations. As a Slovak learner, again, I think it impossible. Even for a country of 5 million people, there are over thirty dialects (not counting sub-dialects) in Slovakia. My own level at the language is affected by the fact I live in an area with a very strong dialect (Zahorie), plus I use Czech (south Moravian dialect) on a weekly basis, which jumbles my vocabulary in both languages somewhat.

it would be mandarin .I think.hahaha

Have you ever think it was good for all world to talk to one langauge?