I am not able to understand the subject-verb agreement concept in the below sentence.

what is much more difficult to determine is the personal reason Locke wrote the Treatise, the changes he might have made to his first version, and the extent to which the published version coheres with Locke's intentions

Now there are two 'is' in the original sentence. In 'what is much more difficult to determine' , what does 'is' correspond to (as in what subject). And the 'is' after determine corresponds to what subject.

My thought - Since there are three reasons that are given as difficult to determine , i felt that the sentence should read as -

what is much more difficult to determine are the personal reason Locke wrote the Treatise, the changes he might have made to his first version, and the extent to which the published version coheres with Locke's intentions.

Where am i making a mistake.

I really thank you for helping me on this.
Hello, Guest. Emotion: smile

Yours is a particular type of sentence called "pseudo-cleft sentence". I've been thinking how to explain the use of the second "is" for a while now, and I've come to the conclusion that I will both post a paragraph from a book and add my own comment to it.

The following sentences are from "A Grammar of Contemporary English", by R. Quirk at al:

"What we need is more books."
"Good manners are a rarity these days."

And this is what you read in the book about subject-verb agreement in these sentences:
"For both sentences there are variants in which the number of the verb is in agreement with the complement:
'What we need more are books.'
'Good manners is a rarity these days.'
These are probably ascribable to the workings of 'notional concord', the idea of plurality being dominant in the first and that of singularity in the second."

My comment: one of the reasons for having more than one possibility when choosing the form of the verb is that an "intensive" verb is used: to be. In many cases, the subject and the subject complement can "exchange" positions in the sentence and, when subject and subject complement are different in number, we usually have the verb agree with the subject (in this case the "formal" subject") rather than with the complement.
Also, "what" is ambivalent with respect to number.

In your original sentence, "is" has been used for one of two reasons:
- the parts of the subject complement may have been taken as a unit, so to speak: "What is difficult to determine is ALL THIS", or "THIS, as a group, is what is difficult to determine".
- The verb agrees with the "formal" subject (what...) . This is not uncommon in "pseudo-cleft sentences" (sentences like the one you posted: a single main clause is divided into two units, each with its own verb. They start usually with "what", and they are used for the sake of "focus").

I'd use "are" is the form of the sentence were:
"The personal reason Locke wrote the Treatise, the changes he might have made to his first version, and the extent to which the published version coheres with Locke's intentions are much more difficult to determine."

Please let me know if this is not clear enough? I tried to keep it short and fairly simple.

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Another way to answer, which may or may not be as clear as Miriam's response, is from Celce-Murcia's and Larsen-Freeman's THE GRAMMAR BOOK. They write, "Traditional grammars tell us that when a clause functions as a subject, the subject-verb agreement is singular" (p. 66). Does that work?

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On p. 67, The Grammar Book gives two examples for the quote in the previous post:
"That the children want friends doesn't surprise me."
"What they want is revolutions everywhere."

And this comment follows:
"We do not have survey information on this type of agreement; however, we suspect that the second type of subject clause cited above causes some difficulty -even among native speakers. This seems especially true when the verb is followed by a plural noun phrase."

I'm posting this only for clarification. The Grammar Book is a pedagogical grammar and does not analyse forms as in-depth as other grammars, formal grammars for example, do.

Also, a sentence of the type of "That the children want friends doesn't surprise anyone is not a good example of what I said in my previous post. In that sentence, the use of "dont'" instead of "doesn't" would be incorrect, whereas in the second example from The Grammar Book both "is" and "are" would be acceptable. Perhaps giving both examples together is making an overgeneralisation.

The type of sentence I referred to in my first post to this thread (in which there are choices regarding subject-verb concord) is one in which the subject is not just any clause but what is called a "nominal relative clause".
In sentences where the subject is a nominal "that-clause", on the other hand, the verb will be usually "singular".

Hope it helps.



I came across this post since I have some confusion regarding the emphasis on multiple elements in the second part of pseudo-cleft constructions that begin with "All."

If there are more than one element that "All" is referring back to, does "All" then always take a singular verb?

For ex: All that is present in the hall is the storage and another room. (why is this is in spite of two elements?)

But, All she saw were stars. (This is a plural element and so on inversion becomes Stars were what she saw.)

But could you please explain the first sentence in the example to me?

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