He considers it important to cooperate. vs. He considers it is important to cooperate

Question

I have a friend studying for an English test and she asked me to explain something to her.

In her textbook, the sentence

• "He considers it is important to cooperate." - is marked incorrect, while
• "He considers it important to cooperate." - is marked correct.

I would intuitively use the second "correct" sentence, but I can't explain why exactly. I have looked a bit here and elsewhere online but can't seem to find an answer.

I'd like to avoid telling her it's correct "just because" and instead give her a solid answer.

So why is it correct to get rid of "is" here?

Answer 1

[1] He considers [it is important to cooperate].

[2] He considers it important [to cooperate].

These are just two different ways of saying the same thing, though [2] is much more likely, probably because it is more economical since it uses less words to express the same meaning as [1].

Syntactically, in [1] the expression it is important to cooperate is a declarative content clause serving as complement of "consider".

[2], by contrast, is an 'extraposition' construction with it as direct object and the bracketed infinitival clause to cooperate functioning as extraposed object.

Answer 2

I find it¹ interesting that according to Google Books, 40 years ago consider it necessary, think it necessary and think it is necessary were all equally common. But consider it is necessary has always been extremely uncommon...

I can only assume the significant decline in use of is after think is because more people have started to apply the same idiomatic preference to think that they'd always applied to consider anyway.

As to why consider rarely occurs with a "tensed verb" clause, I think it's probably just that consider is a relatively "formal, upmarket" verb compared to the "everyday" verb think.

Consequently, I consider it likely the relatively "literary"² construction illustrated by this very sentence was always much more closely associated with consider than with think.

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Obviously OP's friend's cited textbook should be thrown in the dustbin, since it erroneously conflates "idiomatically less common" and "syntactically invalid".

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¹ Less commonly (but certainly not "unacceptably"), I find it is interesting... But more commonly (more "often" and more "colloquially") I think it's interesting...

² This type of construction is declining in English, but I think even though learners should normally avoid using it themselves, they probably do need to understand how it works. I won't go into details about it in this answer, but here's what I wrote 10 years ago on ELU.

Answer 3

The verb to consider when it means "to hold an opinion about something or someone" takes an object {the thing or person the opinion is about} and an adjective phrase [the opinion]:

He considers {drinking plenty of water} [essential].

We can also shift the order of [the opinion] and {the thing the opinion is held about} by using the dummy pronoun it and converting the thing the opinion is held about to an infinitival clause:

He considers {it} [essential] {to drink plenty of water}.

The dummy pronoun it is just a proxy for to drink plenty of water.

I'm using the sloppy word "thing" above but drinking water is actually a behavior, something people do. But the thing the opinion is about can actually be a thing (like a car) or a substance (like a beverage) or a person and in that case the opinion can be presented as a noun-phrase:

He considers {the Land Rover} [a bucket of bolts].

He considers {beer} [a necessity].

He considers {the politician} [a fraud].