Comparison between there and demonstrative pronouns

Question

Comparison between there and demonstrative pronouns

Who claim there is a subject \ question tag ?

Though many books apparently tell that ( there or here ) is never the subject, but the noun that follows, some people still stick in their minds agreeing ( there ) = subject and their evidence is that ( there) = the subject in the question tag ?

The idea is not so, it is just special rule (( The matter is not only with there )) ?

Here are examples :

1- There is a cow , isn't there ?

2- This is a cow , isn't it ? Why we don't say [isn't this] ?

3- That is a cow, isn't it? Why we don't say [isn't that]?

4- These are cows, aren't they ? Why we don't say [ aren't these ] ?

5- Those are cows, aren't they ? And not aren't those ?

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Consider the following examples :

This is yours, isn’t it? Not isn't this

Those don't work, do they? Those 100 % = subject

However, we don't say : Do those \ are those

Only one thing I want to add; to say dummy or real this is not the case. If it is beyond the grammar which is correct grammar and which is incorrect. There are always exceptions with the English language (( People, since ancient time, have used the language so )) The photo below clears it

Answer 1

The "There is" and "There are" constructions are a little bit special.

Your observations are correct. Normally in tag questions, we don't repeat the subject but use a personal pronoun

John is a builder, isn't he?

This is an apple, isn't it?

As you see, the subject is replaced with a personal pronoun whether the subject is a noun, or a demonstrative pronoun.

However this isn't done with there

There's a cat in the garden, isn't there?

This is just how English expresses existence. With a dummy subject "There", a form of the verb "be", and the semantic subject delayed to the complement of the sentence. The oddity of this construction can be noted by comparing it to other languages. Most express "There's a cat in the garden" with the much more "logical" structure like "A cat exists in the garden". That's logical, grammatical, but quite non-idiomatic in English.

So "There is" is a peculiarity of English grammar. It has a special rule for tag questions, but that's not the most peculiar thing about it.

Answer 2

[1] There is a cow , isn't there?

[2] This is a cow , isn't it ?

[3] That is a cow, isn't it?

[4] These are cows, aren't they?

[5] Those are cows, aren't they?

The rule with interrogative tags is that if the anchor subject is a personal pronoun, repeat it; otherwise take the anchor subject as antecedent and select the appropriate personal pronoun. In your examples [2]-[5], the demonstratives "this", "that", these" and "those" are not pronouns but determinatives, which explains why we do not repeat them but instead use the appropriate pronouns, in this case "it" and "they".

But "there" in [1] is a pronoun, which explains why it is repeated in the tag.

Note: the demonstratives when used as independent determiners, as they are in your examples, are a special kind functioning as 'fused determiner-heads', i.e. they are functioning simultaneously as both determiner and head (roughly, "This x is a cow", where "x" is interpreted deictically).