Teacher Discussion Forums

The recession has hit the Beauchamp family this Xmas. On Xmas Eve, Daddy looked in the the closet where the presents were stored and turned to his better half and asked, "Is this all the presents we have for the kids?"

The concept is that he is looking at the sum total. Thus he uses Is this as opposed to Are those...

Another example. A teacher looks at the cars gathered to transport the class on a field trip. "Is this all the cars?" he asks disappointedly. It seems more natural to me than Are those all the cars...

The coach holds up a bag of hockey pucks. "This is all the pucks we have so don't knock them over the boards."

Can we use this is with the plural based on conventional usage or is it always going to be an error?

The indefinite pronoun "all" can be singular or plural (uncountable / countable). See http://englishplus.com/grammar/00000027.htm

"All is well."
"All of the money is gone."
"All of the students are here."

I'd say that your examples are conventional errors. They are commonly made because subjects and predicate nouns are often not in agreement with respect to number in informal speech.

The phrase "Is this all" is often followed by a relative clause, "Is this all that we have?", but when a prepositional phrase complements "all", the pronoun "all" can become plural, and the verb needs to reflect that. In all of your examples, "all" is a determiner and not a pronoun, but the same principle applies. The verb and subject should be in agreement with the predicate noun whenever possible.

"Are these all the presents?"

"Is that all there is, is that all there is
If that's all there is my friends, then let's keep dancing"

Seems to me that they are really thinking of the amount so that there is a kind of ellipsis.

"Is this (amount of presents) all the presents we have?"

Yes, I think that's the implied meaning too. It adds emphasis to the small amount to use "this" rather than "these". You could explain it to students as an ellipsis that occurs in informal speech, but I would let them know that in business correspondence their employer probably wouldn't want them to write something like, "This was all the samples that the company sent us."