I humbly suggest that Joel misread. I don’t think this is correct.

Let me try to make this clear for you.

ボビーさん 　は　すし　を　たべます。
Bobby will eat sushi.
… would be the answer to…
ボビーさん　が　なに　を　たべますか？
What will Bobby eat?

ボビーさん 　が 　すし　を　たべます。
Bobby will eat sushi.
… would be the answer to…
すし　を　だれ　たべますか？
Who will eat sushi?

First case : you don’t need to emphasize ボビーさん, because the person who asked the question introduced him as the topic using が. What’s important in your reply is the part that actually gives the person the information they want (i.e. that すし is what Bobby will eat). That’s what I guess Koichi means when he says that は emphasizes what comes after.

Second case : the person who asked the question didn’t introduce any topic. A topic is something that is defined and “who” is, in essence, undefined. Besides, Bobby wasn’t mentioned. So you will have to use が to introduce ボビーさん as the topic of your reply. This time, the important part of your answer comes before the particle. They know sushi will be eaten, what they want to know is by whom. That would be ボビーさん.

So, as for your example, there are two possible situations:

-These people weren’t talking about food before.
The person who asks the question has to use が to introduce たべもの as the topic. Once it’s done and until the topic changes, が won’t be needed anymore for たべもの. So は should be used in the answer （and the following sentences）.

-These people were already talking about food.
Since they were already talking about it, たべもの is clearly the topic. が is not needed – it might have been used sooner in the conversation, though – and both persons should use は.

Joel is obviously welcome to correct me if I said anything wrong.

O… kay… That’s… funny.
That was my first reaction. Because none of these concepts are even mentioned in the course.

So, I researched a little bit about this issue, found some useful stuff. I went through some of your posts too, and I’d like further clarifications, if you don’t mind.

About this particular example… (1) You don’t use が in the question because たべもの is a generic term, and you don’t use は in the answer because ot its contrastive function, is that correct? (2) Is it also correct that you would omit the subject in most cases anyway and just answer はい、すき　です?

(The answer to this whole last part might be the answer to the very last question, so I suggest you read it in one go instead of stopping to answer an individual question.)

Now, I read about how you should not say め　は　きれい　です to a girl, because it would imply that her other features are not that great.
(3) Is this contrastive inference context-dependent? I mean, I understand that if a girl asks you if you think she’s pretty and you go め　は。。。きれい　です it will feel like five seconds of awkward silence followed by an obligatory compliment, but what if she didn’t ask your opinion about anything and you’re just saying that out of nowhere?

Finally, (4) what if she asked about her eyes specifically (and you choose not to omit the subject)? I suppose め　は　いろ　は　きれい　です will have the same forced compliment feeling, implying that maybe her eyes have a weird shape or something, but since she made her eyes the topic when she asked, couldn’t you say め　は　きれい　です without implying anything? In the same context, wouldn’t it also be okay to say (め　は)　いろ　が　きれい　です?

Or, last minute theory, is it just that you have to use が whatever the context is, because the topic is never め , but rather the omitted あなた / きみ, which would be the word with a は attached to it, making all subsequent は’s contrastive?

Thanks a lot for your time.
And your patience. :)

• This reply was modified 8 years, 3 months ago by  Brook.

Cool! :)

It would have bothered me to have made you read all of this, still not get it, and have to come back again with another batch of questions on the subject.

The last sentence I was asking about was actually (め　は)　いろ　が　きれい　です but you made it quite clear that it would sound like an acceptable “Yes ! They have a pretty color!” while いろ　は　きれい　です would sound more like “Well… They have a pretty color, I guess.”

Anyway, thanks again.

I’d like to know about the book you quoted from to explain the use of は in that other thread. Is it A Dictionary of Basic Japanese Grammar by Seiichi Makino? Would you recommend it to a beginner such as myself? I mean, besides the fact that owning it would make me ask you less questions… :)

So Joel did misread!
Congratulations, me: I was kind of right in some kind of way.
Ha! Ha! Ha!

(Please note that I absolutely didn’t notice this myself either. My own ignorance was the only reason for my mistake.)

Thanks for the tip, Joel. I planned to read it as a whole too. Since it’s supposed to cover the basics, I’m guessing everything in it is pretty common and therefore very useful.