Writing style: When to use "there is"?

In which situations would you choose one of these sentence structures over the other?

There is a blue cat on the piano.

A blue cat is on the piano.

There exists a blue cat on the piano.

1: I’m describing the room in general. The cat isn’t much more important than a flowerpot.
2: I may be talking about more stuff involving the cat.
3: I’m 15yo and about to suffer an attack of Angstius Maximus. 3, option b: I’m sick of practicing Roberto Carlos’ song about “the cat that’s sad and blue” on the piano. I’m seriously considering throwing the partiture at Mr. Carlos, perhaps followed by the piano.

“When” is always subject to context. What are you writing? Who are you writing it for? Is it intended to be formal or informal? Fiction or nonfiction?

There is no one right answer.

No one right answer exists.

One right answer? Whatever.

If I’m doing writing I almost never write in the present tense, and I certainly wouldn’t be writing in the present tense about something so transient as the location of a cat. Which means that this is almost certainly dialogue voiced by a fictional character. (The cat being blue supports this.) And given the rather blunt, simple phrasing, I can’t help but read this as a spontaneous comment made due to surprise at what the fictional character was observing. The difference between the two statements is in what is prompting the surprise. In the first the character is surprised by the fact that there’s a blue cat there at all. In the second the surprise seems a bit more centered around the fact the cat is on the piano, specifically.

This one, on the other hand, is clearly the premise of a formal logical argument. ∃x: IsCat(x) ∧ IsBlue(x) ∧ IsOnPiano(x).

Actually, this is clearly the punchline of one of those engineer, physicist, and mathematician jokes.

Can’t really disagree with any of the responses, but I think Nava pins it down the most specifically. There is a subtle difference in emphasis between the first and second forms. While they appear to be saying the same thing, the linguistic spotlight is directed at the entity that comes first. The first one seems to be about the piano, or perhaps about the room or the house, or about someone seeing things. The second puts the emphasis on the cat, and we expect to hear more about it – what will the cat do next?

Thus if I was writing a story about someone imagining a blue cat on the piano, and the next moment it’s gone, and he sees a vase of roses in its stead, I would use the first form. If I was writing a story about the adventures of a blue cat, I would use the second form.

It’s hard to imagine any context where the third form is appropriate other than a logical or philosophical proposition, but those generally deal with logical abstractions rather than everyday objects, and such forms are used for maximum precision in stating the premise. They’re not used in everyday speech.

The cat at the piano is blue?

Is that a blue cat at the piano?

Blue, which is an odd color for a cat, is sitting at the piano

That blue cat is at the piano again

I know…off topic/moot but trying to be funny again! :slight_smile:

Is it delftwear? Or cobalt glass? Because the Franklin Mint had both in its cat figurine series.

“A blue cat is on the piano” belongs in a story by Alain Robbe-Grillet.

a hijack: “Blue”, in reference to a cat, refers to a slate gray coloration. Look up pictures of British Shorthairs, Russian Blues, or Korats.

First there is a blue cat
Then there is no blue cat
Then there is.

(sorry, Donovan.)

A jazz group is playing. There is a blue cat on the piano. The rest of the group seems lively, however.