"Humanity must learn Esperanto."
Translation:La homaro devas lerni Esperanton.
Why volitive is considered to be a "must"? I thought it's a bit too strong for volitive.
I had come here to say the same thing. I understand it as more of a hypothetical suggestion than an absolute must.
I would say "la homaro".
"Homaro devas lerni Esperanton" I would interpret as "A humanity" or "A group of people" (one of many) must learn Esperanto, but if you mean the one single humanity, the one that you are thinking of and that you expect me to know about, I would use "la homaro" because it seems definite to me, even if English doesn't use the definite article there.
Thanks! I'm still not exactly sure when one would use homaro without the article though. :p
Basically, very infrequently. Imagine a fictional setting where many similar groups of human-like species exist across several planets - one could then make some general statements, perhaps, about "a humanity" in general (e.g., homaro nur estas tiel bona kiel sia moralo). It might be appropriate to say homaro in real-world philosophical questions as well, where we consider the factors that gave rise to humanity as we know it and compare them to all theoretically possible worlds and outcomes.