Could anyone explain the possible meanings of would+have+past participle with suitable examples?
Like,'For the most part of the book consists of several series of revelations and visions presented in symbolic language that would have been understood by Christians of that day, but would have remained a mystery to all others'.
To understand "would have been understood", you need to understand "would have been", and hence "would" and "have been".
I'll assume you have some idea of the basic concepts of these words.
Let me reduce the sentence, "The book was in symbolic language that would have been understood by Christians."
This is the passive form of the active sentence "Christians would have understood it (while others would not have)."
Now, this is an assumption made by this historian. If he knew for certain and had evidence, he would say "Christians understood it" (It was understood by Christians - passive). But he is making an estimation, based on all he knows about the history, that "Christians would have understood it" - they must have understood it. He cannot imagine them not understanding it.
This is not a conditional sentence. He's not saying, "Christians would have understood it if they could read."
Let's look at some easier examples:
A: Your wife swore at me yesterday!
B: Oh, she wouldn't have done that! (It's very unlikely that she would do that.)
Policeman: "WHat were you doing on the afternoon of June 12th last year?"
Suspect: "Oh, I would have been as work." (He cannot say for sure, but that's the most likely possibility)
There's a start. If you are still having trouble and if no one else chimes in with a better explanation, I'll have another go tomorrow when I'm not so tired.