Can 'nothing' ever be preceded by a plural verb?

Question

I've had it drilled into my head that nothing is always singular, since it's essentially another way to say 'no thing'. However, in the following sentence, I'm having trouble ascertaining whether the preceding verb should be singular or plural:

There are nothing but liars in here.

Is this sentence acceptable? I'm inclined to believe that nothing is being used as an adverb rather than a pronoun, so it is correct to use 'are' rather than 'is'. Here's another example sentence:

They are nothing but petty thieves.

In this case, since the subject is simpler, it becomes more clear that the plural should be acceptable. Am I understanding this correctly?

Answer 1

The are applies to liars, not to nothing here.

Did you notice that you have but in both your examples? Nothing but as a phrase is used here in an idiomatic sense. We can reread the sentences as:

There are only liars in here.
They are just petty thieves.

That's how it is, I believe.

Answer 2

‘They are nothing but petty thieves’ is grammatical because, as others have said, they means those people the speaker is calling petty thieves. In the other sentence, ‘There are nothing but liars in here’, nothing but could, as in the first sentence, be replaced by just or only. But I wonder if it wouldn’t be more likely to occur as ‘There’s nothing but liars in here’. As noted in ‘The Cambridge Guide to English Usage’, there’s seems to be in the process of becoming a fixed phrase, regardless of whether the context is singular or plural.

Answer 3

To answer the question in the title, nothing can certainly be preceded by a plural verb. We should distinguish two types of situations where this might occur; one is much more clear-cut than the other.

Sentences where "nothing" is not the subject of the verb, so the verb agrees with another noun phrase that could be plural

Noun phrases linked by the verb "to be" are not treated equally in English: only one can play the role of the subject. The other is merely a "complement" or "predicative noun". The verb "to be" agrees in number with its subject, not with its complement, so regardless of whether nothing is singular or plural, only plural agreement is appropriate in

They are nothing but petty thieves

because nothing here is only the complement of the verb (or if you prefer, of the subject); the subject of the sentence is they, which is indisputably plural.

As you say, it's clear to anyone that "They is nothing but petty thieves" would be wrong. So in fact, in this circumstance, nothing actually HAS to be preceded by a plural verb. It could also be preceded by a plural verb if it takes the role of grammatical object (this is probably also obvious after being pointed out): we have to say They ate nothing, using the plural verb "ate" to agree with the plural subject "they".

Sentences where "nothing" is the subject, but maybe would take plural agreement

There are nothing but liars in here.

A "There are..." sentence like this is a more complicated matter. Despite the surface similarity, it doesn't necessarily have the same structure as a sentence starting with "They are...". Traditionally, the there of the existential construction is NOT taken to be the subject of the clause; instead the following noun phrase is the subject (which is why we normally select "there is" or "there are" based on the number of the following noun phrase).

In a situation like this, the grammatical number of nothing is indeed relevant. There's another question specifically about this issue: Is “nothing but birds and a few insects” singular or plural?