What is the assumed subject of -u form verbs

Question

Something that came up in an answer to my previous question was, what is the assumed subject of a u-form verb, which I incorrectly assumed to always be vi. When I say Kuru!, or Sidiĝu! I really mean a command directed towards a specific person. But it was mentioned that Pluvu! is valid and I am really meaning Let it rain!, rather commanding somebody specific to start raining. Similarly, Estu! can mean Let it be so! The question then is, how do I get this right. What if I want to command the rain god to start raining. Pluvu! seems correct then. Is this simply something to get out of context? If I am yelling at Hamlet during the play (a sure way to get kicked out of the theater), I want to yell Estu!, and I do not mean Let it be so!, I really mean Be!.

So is it always context? Or should I say Vi estu! if I mean Be!. And if I want to say Let it rain! in the presence of a rain god and I don't want it to be interpreted as a command, should I say Ĝi pluvu!? Or is Vi estu! a weaker statement such as Let you be?

Or is it correct to still think of both Pluvu! and Estu! both as commands, although normally directed towards some metaphorical entity, unless directed specifically towards the rain god and/or Hamlet? In English when I yell Rain! I am saying Let it rain! but more forecfully, so it is a command towards some metaphorical entity. On the other hand, if I, in English, say Be! I do not mean Let it be so!

Answer 1

Unless a subject is specified, the implied subject of a u-verb is usually vi, as you had thought. When a verb can be used impersonally, however, such as pluvi or esti then it's possible that there is no implied subject.

The trouble, it seems to be, is with esti which can be used both personally and impersonally. This is not just a problem with estu but also comes into play with other forms.

• Estas bone havi amikojn. It is good to have friends.
• Estas problemo en mia respondo. There's a problem in my answer.

One might be tempted to ask whether estas like this means "it is" or "there is." The answer is -- read the whole sentence and try to understand it. The same thing applies if the verb ends in -u.