@Brus - You rewrite my sentence by scattering a few commas around in it: "the subjunctive is the ultimate polish, which, once mastered, allows the user the right finally to claim that he has learned the language."

It's not just a few commas, it's the logic of the language and its structure.

I would be very surprised about the excellent level of your English writing if you are not a native speaker of English, but quite curious about the way you approach the subjunctive mood if you are a native speaker.

@ Warsaw Will - If I'm not so sure about my course of action I'd use 'could, may' or 'might', but not 'would'

Agree that most people would do this, but not all, especially when accompanied with the if clause.

@ Warsaw Will - "If I won" (with real past meaning) show no such uncertainty.

Depends on what you would win, if it's a lottery, as the chance of winning is so slim, even when the if clause has the real past meaning, "If I won" does show some sort of uncertainty. But anyway, you still have a chance to win when if clause refers to the real past meaning, so it's not imaginary present.

@ Warsaw Will - I'm really only interested in how conditionals are used in everyday life, not weird and wonderful scenarios where the interpretation is stretched to the limit,...

That's why I disagree with the "I can't remember if I was the prime minister" scenario. The lottery winning context I thought of, is not that common in daily life, but not very weird and wonderful. So the difficulty for a teacher lies in how you would teach. This is extremely true when it comes to the subjunctive teaching in ESL. I find myself in good agreement with Brus in the fact that "the subjunctive is, as the conversation above indicates, complex and not to be covered in too much hurry"

@Brus - the subjunctive is the ultimate polish which once mastered allows the user the right finally to claim that he has learned the language.

In order to learn the language, it seems to me there is a lot more to master than the subjunctive, which includes the distinction between "that" and "which". Other than the questions asked in the last post, I would read the above sentence as:

"the subjunctive is the ultimate polish, which, once mastered, allows the user the right finally to claim that he has learned the language."

To be honest, it's a bit complicated sentence.

Brus - the subjunctive is the ultimate polish which once mastered allows the user the right finally to claim that he has learned the language.

Should it be "which (is) once mastered"? Can you master a polish? Or the craft of polishing?

@Sundy - Though I would have to agree that your interpretation works in your proposed context, but that's not an usual context.

Keep in mind that I have said this already.

If I say "If I was the prime minister, I'd change the law" to my colleagues tomorrow, how would they interpret? Sure, "If I was the prime minister" will be taken as imaginary assumption, which is far more common than your context.

@Brus - You allow that I could give (you) poor marks of English (sic), and indeed I I fear I must.

I don't really care about what you must do. But we are discussing the logic behind a language, not anything else.

I meant:

would" works as well in 'If I won the lottery, I'd buy a new house', in which "would" implies that there is less possibility of buying a new house as other factors may come into play.

@ Warsaw Will - Well, we would in British English at least. I know Americans don't use present perfect as much as us, but if it's a real condition, you'd (they'd) still use 'will' in the result clause.

I would think simple past tense also works here. When there has been no change to the situation since the time that the past tense indicates, simple past would mean the same as the present perfect. This is the reason why American tends to use simple past in many contexts where this condition is met.

"would" works as well in 'If I've won the lottery, I'd buy a new house', in which "would" implies that there is less possibility of buying a new house as other factors may come into play.

@ Warsaw Will - "Ideally, it would be perfect if we could create a subjunctive form of verb for every verb in English" - that would be to reverse history and go against what you were saying earlier.

Look at the last part of what I was saying: "which, however, would result in an unrealistic and unpractical situation, too many forms of verbs."

@ Warsaw Will - "If he managed to finish that report last night, we'll be able to get it to everyone today".

In a context where typing the report may need to be done by another person as "he" was only the report writer, "we'd be..." works, especially when typing may take some time.

@ Warsaw Will - My point, though, is that Unreal past (subjunctive, for those who prefer it) is exactly the same as Real Past for all verbs except one, and for only two persons of that one verb, 1st and 3rd singular of 'be'. I can see no logical reason why a different form is thought necessary for those two persons of one verb when we have absolutely no confusion in all other cases. It might sound more refined, but that's about all.

Yes, there is no logical reason that a different form is necessary for only two persons of that one verb, 1st and 3rd singular of 'be'. In Chinese, there are no such forms of verbs, only one fixed form for every verb. But subjunctive is a mood existing in every language, I guess. In Chinese, there are other words that explicitly propose an imaginary situation, something like " listen up: I am doing daydreaming now, I am the prime minister, I will change the law." Of course, these words are quite different in a sense that they can express different emotions or moods.

Humans have so much confusion in conversational communication in terms of the language itself. English works in its own way. Ideally, it would be perfect if we could create a subjunctive form of verb for every verb in English, which, however, would result in an unrealistic and unpractical situation, too many forms of verbs. The problem now is that the verb needs a form in a sentence in expressing subjunctive mood, which will definitely confuse with other forms of verbs such as past and future tenses. Luckily, the context where the conversation is taking place will resolve the ambiguity. That's why I would expect that even "I was you" would substitute "if I were you" in the future, as the assumption of "I am you " will be never truthful in our context of human's world.

@ Warsaw Will - "If I won the lottery, I'd buy a new house" - can you put a different interpretation on that?

Yes. Assume this context:

You were so tired and went to bed last night before the lottery winning numbers showed on TV. In the morning after you get out of bed, you hold your lottery ticket in hand, ticking it in front of your wife, saying:

"If I won the lottery, I'd buy a new house."

You are referring to the real past. But since your wife doesn't know you didn't have a chance to check the number as usual, she interprets "if I won the lottery" as to refer to the present, hence meaning an imaginary situation.

She then might say to you : "Don't keep daydreaming."

You further explain: "I didn't have a chance to check the number as I went to bed earlier last night. I still have a chance to win." So now she understands that "if won the lottery" means a real condition.

The context is a key.

You go on the street and ask the ordinary people how they would feel if somebody says he /she can’t remember if he/she was the prime minister before. People would say: “it’s a bit wired. I would never forget if I was once the prime minister.” So when you say to, again, ordinary people that “if I was the prime minister,..” you would be taken as to mean an imaginary situation of being the prime minister.

Demotic usage based on their contexts determines the life of a language, eventually, not the contexts thought of by linguists in pure linguistics.