Max M. answered 04/19/19
Harvard Literature major with 20 years of coaching writers
Let's do the easy part first, and disambiguate terms.
Prose is normal writing--full sentences, no meter, no rhyme, just saying whatever you want to say until you're done.
Verse, broadly speaking, is, well, not that. While there are a lot of different kinds of verse, from haiku to sonnets to ballads to Whitman or Ginsburg's long, unrhymed lines to e. e. cummings, etc., what they all have in common is that the text is structured so as to add another layer of meaning. I'm happy to talk more about that if you want to work together.
But for now, that's super general.
Rhymed means that at least some of the ends of lines rhyme (I'm assuming I don't need to define rhyme). Maybe pairs of lines rhyme with each other (AABB), maybe alternate lines rhyme (ABAB), maybe not all lines rhyme (ABAC), but something.
Iambic describes a meter, or a rhythm, that's kind of like a heartbeat. It goes "ba-BUM."
Pentameter means that each line has five stressed syllables in it (there's a minor exception to this, but it's a pretty solid general definition). So a line of iambic pentameter would have five iambs in it. It would go "ba-BUM ba-BUM ba-BUM ba-BUM ba-BUM." And so rhymed iambic pentameter would mean it's written in lines like that, and they rhyme.
Blank verse means verse that has a meter, might be iambic pentameter, might be something else, but no rhyme.
(And it's not relevant for this question, but free verse is poetry that doesn't have rhyme or meter. Whitman and Ginsburg are often good examples. Not a lot of poets before the 1900s were doing it.)
Ok, so based on all that, what's the structure of this passage?
Is it structured? Are there line breaks in the middle of it for example? Clearly, yes, you've indicated them. So, not prose. Do any lines rhyme? Doesn't look like it to me. Is it iambic pentameter? Try reading the first line out loud...does it fit into the "ba-BUM ba-BUM ba-BUM ba-BUM ba-BUM?" rhythm? I think so: "a PLAGUE uPON you, MURderers, TRAItors ALL." Except for the two unstressed beats at the end of "murderers," it works...Doesn't sound weird or forced if you read it like that, right? Ok, so iambic pentameter that doesn't rhyme...that's going to be blank verse.
(If you want to get into discussions of why it does or doesn't matter that it's blank verse and not something else, I'm happy to talk about that too).
So, onto the thematic question, a much more open-ended one. Lear is grieving over his dead daughter. At the beginning of the play, he banished her for not giving a big speech about how much she loved him, but then he finds out too late that she was actually the only one of his daughters who did love him. They have a brief reunion, but then they're captured by enemy soldiers, and she's killed before he can save her.
Looking at what he says, is this a speech about compassion? Hard to say, depending on your understanding of compassion. He's certainly been brought down from the pedestal he started the play on, when he wasn't interested in anything that wasn't about how great he was, so maybe he's learned some compassion, or anyway some appreciation for kindness and patience. On the other hand, compassion means feeling for other people's suffering, and Cordelia isn't suffering--she's dead. Lear's sad about that, to say the least, but is compassion the right word? I'm not sure, but it feels a little off-base to me. And he starts the speech cursing other people--is that compassionate? He's yelling at them for letting her die, but he's just as guilty as they are. And he ends the speech by talking about killing someone. Someone who was hurting her, but killing is killing. Is that compassion? I'm not trying to steer you towards one answer or the other here, more to get you to see how your answer will depend on the different ways you might look at both the text and the theme.
Same goes for truth, though this might be a little easier. One big truth he understands now is that Cordelia did really love him, which he couldn't see at the beginning of the play. Or is the fact that he says "What is't thou say'st?" a sign that he refuses to accept the truth that she's dead, and he's just switched from one kind of denial to another?