delta Wrote:Exactly, 今日は, today in particular or today as opposed to other days. Another good example is 二時間は勉強した, I studied at least for two hours (no less).
It can also have the related sense of ”studied as much as 2 hours!". This implies some previous knowledge of the amount hours and the speaker is emphasizing the amount. So it's similar to emphasis も.
It's probably fair to say that the various functions of は all convey (to varying degrees) the implication that no claim is being made about whether the comment applies to likely alternatives. But contrastive は and emphasis は have some functional and syntactic differences, so it might be good idea not to merge them completely in your mind. (For eg, Vては can emphasize V in the sense that V is repeated - eg "he just eats and eats" or "every time he eats, he...". V is kind of being singled out, but the contrastive sense isn't strong; it isn't trying to imply much about other Vs.)
drdunlap already mentioned that different functions of はcan overlap/co-occur (here, emphasis and contrast) and that emphasis は and も share similar functions. Another function in your sentence (and in the earlier 助かる sentence) is to mark which element is being negated ('negative scope'). (English uses emphasis for this: "Bob didn't go school YESTERDAY".) It's a subtype of emphasis perhaps, but it still plays a grammatical role. Some teachers claim sentences sound less natural without them. An extreme eg: は is rarely left out of ~ではない (じゃない) from ~である.
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For my own learning, I'd be interested to know what made は in this sentence difficult to understand. Was it that は marking an adjective, verb or adverb is less familiar than when it marks a noun phrase? Or was it the は、も combination?
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More generally, I think beginners might want to at least take note that "topic marker" is a convenient label for the particle は, but it doesn't describe the various functions of は. They shouldn't listen to the mistaken advice given by someone in this forum that " は only ever marks a topic -what the rest of the sentence is about- and any other explanation is nonsense". (lol) If they do, they might be confused when they encounter other uses, it will take longer to develop a sense for the different nuances conveyed by は, and they won't understand why some of their own sentences are grammatically incorrect.
There's no need to memorize anything or read anything complicated. A simple awareness that the different uses exist will help people to notice them and to fine-tune their understanding more quickly as they read and listen.
Edit: moved unrelated comment to a separate post.
Edited: 2012-12-24, 4:06 pm