Problem with choosing のは or は with と思います


So in my textbook there are examples like

> あまり便利じゃないと思います  
>  いいと思います

But I was wondering, how would you say something like "I think it's ok to eat
food". From my knowledge it should be something along the lines of:

> 食べ物を食べるはいいと思います

But I'm certain that this is not okay, any help is appreciated.




The issue of choosing between のは and は has little to nothing to do with と思います.

The grammar of these constructs is as follows:

  * < _sentence_ > と思います
  * < _noun phrase_ > は

In your first two examples:

> あまり便利じゃないと思います

The _sentence_ is あまり便利じゃない: "it is not very useful".

> いいと思います

The _sentence_ is いい: "It is good".

Notice that even in English with "I think it's ok to eat food", the "to eat
food" is itself not a sentence. It's a noun phrase formed from an infinite of
the verb "eat". (In English we might say "the verb to eat" but this is
technically not correct.)

If you have some sort of verbal phrase that you want to say something about,
you've first got to nominalize it. Most frequently you will choose one of
either こと or の. Once the verbal phrase is nomialized you can put it in a
sentence and refer to it like you would just about any other noun.

> 食べ物を食べる

This means, "Someone eats food".

> 食べ物を食べるの

This means, "To eat food" (an infinitive phrase in English) or "Eating food"
(a gerund construction in English). Now we can say something about "eating
food".

> 食べ物を食べるのはいい

It's good/OK to eat food.

And now you can tack on と思います to get the idea in there that this is what you
think.

> 食べ物を食べるのはいいと思います

