Using は before 欲しい instead が


I was doing some exercises and the book that I'm using translated:

> I don't want shoes

to

> 靴は欲しくないです

I answered using が particle instead は, since, as far as I know, I should use が
before 欲しい. So why did the book use は this time?

I imagined that the reason is to make a contrast/comparison that は provide. Is
that why?




_**" I want xxx." vs. "I do not want xxx."**_

When you want something, you will generally say:

> 「XXX + **が** + ほしい」

and when you do not want something, you will generally say:

> 「XXX + **は** + ほしくない」

**The only times you can and must use** 「XXX + **が** + ほしくない」 **is when it is
used in the if-clause or relative clause.** Thus, it is correct to say:

> Relative Clause:「靴{くつ} + **が** + 欲{ほ}しくない人は靴屋{くつや}へは行かない。」
>
> "A person who does not want shoes would not go to a shoestore."
>
> If-Clause:「靴 + **が** + 欲しくなければ、なんで靴屋に来たの？」
>
> "If you do not want shoes, why did you come to a shoestore?"

Moving on...

_**The contrastive 「は」**_

This is essentially a different topic from what has been discussed above.

It is correct to say:

> 「靴 + **は** + 欲しくない。」

when you do not want shoes but want another thing. Thus, you can say:

> 「靴 **は** 欲しくないけど、ジーンズ **は** 欲しい。」

That is a pair of contrastive は's. "I don't want shoes, but I want some
jeans."

> I imagined that the reason is to make a contrast/comparison that は provides.
> Is that why?

No, as I stated above. We are talking about two different things. One is
affirmative vs. negative. The other is contrastive.




_**" I want xxx." vs. "I do not want xxx."**_

When you want something, you will generally say:

> 「XXX + **が** + ほしい」

and when you do not want something, you will generally say:

> 「XXX + **は** + ほしくない」

**The only times you can and must use** 「XXX + **が** + ほしくない」 **is when it is
used in the if-clause or relative clause.** Thus, it is correct to say:

> Relative Clause:「靴{くつ} + **が** + 欲{ほ}しくない人は靴屋{くつや}へは行かない。」
>
> "A person who does not want shoes would not go to a shoestore."
>
> If-Clause:「靴 + **が** + 欲しくなければ、なんで靴屋に来たの？」
>
> "If you do not want shoes, why did you come to a shoestore?"

Moving on...

_**The contrastive 「は」**_

This is essentially a different topic from what has been discussed above.

It is correct to say:

> 「靴 + **は** + 欲しくない。」

when you do not want shoes but want another thing. Thus, you can say:

> 「靴 **は** 欲しくないけど、ジーンズ **は** 欲しい。」

That is a pair of contrastive は's. "I don't want shoes, but I want some
jeans."

> I imagined that the reason is to make a contrast/comparison that は provides.
> Is that why?

No, as I stated above. We are talking about two different things. One is
affirmative vs. negative. The other is contrastive.

