1. All you should do is study hard.

  2. All you should do is to study hard.

Is the one with to correct? When should I use to like that?

  • 2
    Those are infinitive clauses and to is a marker of the infinitive; it is often deleted in All-clefts and What-clefts like the ones you mention. I.e, you can use it or you can leave it out, and it makes no difference; speaker's choice. Here. In other constructions, the rules are different. Dec 26, 2014 at 16:44
  • So both sentences are correct, right?
    – mimi
    Dec 26, 2014 at 16:47
  • And what do you mean in other constructions?
    – mimi
    Dec 26, 2014 at 16:48
  • 3
    For instance, in I want to go to Paris, to may not be omitted before the infinitive go. There are a lot of uses for infinitives; the sentences you mentioned were both Cleft constructions, and they have their own rules. English grammar rules depend on constructions and constituents, not individual words. Dec 26, 2014 at 16:54
  • 1
    @FumbleFingers Hmm. I wouldn't disagree with you there. But almost everyone else would. This is often called an All-cleft. People wouldn't normally regard a The easiest thing to do sentence as an All-cleft - any more than they'd regard a Pseudo-cleft as an All-cleft. Do you think the other link is grammatically more like an All-cleft or a Pseudo-cleft? Feb 4, 2015 at 0:17

2 Answers 2


Short Answer

All you should do is study hard.

All you should do is to study hard.

Both of the sentences are correct. The to is optional here.

Long Answer

The sentence quoted is an example of a pseudo-cleft sentence. A pseudo-cleft has a fused relative construction defining a variable whose value is specified by the foregrounded element. The usual alignment is for the element defining the variable to occur as the subject and the one giving the value as the internal component, but the reverse order is also possible.

What I need is a cool drink. [basic pseudo-cleft]

A cool drink is what I need. [reversed pseudo-cleft]

We can have a non-finite clause as the one giving the value.

What I want to do is (to) call the police right away.

Here the to is optional. Why?

It depends on the verb of the fused relative clause. The pattern of the verb varies. So the cases where to is optional and where it's obligatory are based on the pattern the verb of the fused relative clause takes.

  • Here the fused relative clause is - What I want to do

  • Two verbs are present - want and do

  • After the verb want we must have a to construction.

I want to do it. (CORRECT)

  • I want do it. (INCORRECT)

The pattern after do is

I play cricket. (CORRECT)

I do play cricket (CORRECT)

  • I do to play cricket (INCORRECT)

Given the sentence, "What I want to do is (to) call the police right away", if we follow the pattern of the verb want, we have to use to before call, and if we want to follow the pattern of the verb do, we have to use only call without to.

Similarly the following sentences are correct

1. What would be better is to call them beforehand. [Here to is obligatory. Reason? After would be better, the to is mandatory. Consider the sentence - It would be better to call them beforehand. If we omit to, the sentence would be incorrect.]

2. All they want is to get a house for free. [Here also to is mandatory. Consider the sentence - I want to get a free home. After the verb want we need a to infinitive, as omitting to will result in a incorrect sentence]

3. All the trees need now is watering. [Consider the sentence - All the trees need watering.]

4. What the paper shredder does is tear the paper into small pieces. [Consider the sentence - The paper shredder does tear the paper into small pieces. We can't add to before tear. doing so will make the sentence incorrect.]

Consider the following sentence

What you must do is (to) apply for special leave.

Here to is optional. In fused relative clauses where the verb is do, the to is optional.

When the verb of the fused relative clause has an -ing form, the complement also matches with an -ing form. Illustrated in a sentence:

What I am doing is teaching him a lesson.

The acceptability of this next sentence is doubtful, but it can be interpreted as an elliptical form of an alternative construction involving apposition:

What he has done is spoilt the whole thing.

What he has done is ((this): he's) spoilt the whole thing.

The example above was borrowed from the 1985 reference grammar by Quirk et al., A Comprehensive Grammar of the English Language, section 18.29, page 1388:

Occasionally, such matching of the two verbs is extended to verbs in the perfective aspect, which can have as their counterpart an -ed clause:

  • (?) What he's done is spoilt the whole thing.

This last type is, however, of doubtful acceptability, and instances of it may indeed be interpreted as ellipted forms of an alternative construction involving apposition:

  • What he's done is ((this) : he's) spoilt the whole thing.
  • Your last sentence is perfectly fine! It's not doubtful! :-) Feb 4, 2015 at 0:23
  • @Araucaria Just remembered something I forgot to include in my answer. I actually don't know if I am correct, but google search makes me think I am. Just for confirmation I am asking. If this sentence also correct - What I have done is teach him a lesson? See here it's teach. I think both teach and taught are correct. And this sentence is not correct, I think - What he did was taught him a lesson. It should be what I he did was teach him a lesson. Am I right? Apr 11, 2015 at 13:45
  • Well, kind of. It should have been "what I did was teach him a lesson" Apr 11, 2015 at 15:03
  • +1, for a nice post! :) -- Though, in my idiolect, the verb for the subordinate VP is less constrained, e.g. "What he did was taught him a lesson" would be acceptable, as the pseudo-cleft is understood to have the associated non-cleft "He taught him a lesson". But my idiolect appears to be non-standard on this issue, w.r.t. 2002 H&P CGEL and the 1985 Quirk et al. Oh, well. (cc. @Araucaria )
    – F.E.
    Apr 11, 2015 at 19:07
  • Though, be aware that your answer post is on pseudo-clefts, while the OP's examples are all-clefts. The two types of constructions are related, and your answer does seem to be quite applicable to the OP's question. :)
    – F.E.
    Apr 11, 2015 at 19:40

The idea here is that infinitives following modal verbs do not need "to;" the bare infinitive is appropriate. There is no special construction needed for this to be true. Modal verbs are helping verbs like can, could, should, would, must and may (and others.)

Want, used as a counter example in the comments, is not a modal verb, and so we use the full infinitive with it.

This can get more complicated with phrases like:

I would like to go to the park.

Here the modal verb would is operating on the infinitive like and so the bare infinitive is appropriate. This doesn't extend to the infinitive to go that follows; there it is acting as a noun (an object, specifically.)

  • Are you saying that to is ungrammatical here? Feb 4, 2015 at 0:23
  • @Araucaria It really depends on the construction of the sentence. With the particular wording of the OP's question, it's optional. If it were something like "What I think you should do is (to) go dancing," then both versions of the sentence, with and without "to" are grammatical, but the version without "to" flows better and is far more common in American English. Including the "to" sounds odd and a bit old fashioned. Feb 4, 2015 at 1:53

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .