Not sure if this was already discussed, but I am confused about the use of -ing form/infinitives as complements. I've found in several threads in Stack Exchange that the verb "to be" has to be followed with an infinitive form like in the example:

What we want is to be free.


All you can do is (to) wait for the results.

However, I've found on other resource that verbs in their -ing form are used as complements too, like in this sentence:

The group’s main goal is eliminating poverty.

Even Practical English Usage by Michael Swan states that -ing forms can be used as complements (like: "My favorite activity is reading poetry").

Then I am wondering if the below sentences can be considered correct:

What we want is being free.

All you can do is waiting for the results.

If the above examples are ungrammatical, may I know the reason?

1 Answer 1


All you can do is WAIT. OK

All you can do is WAITING. unidiomatic

What we want is TO BE free. OK

What we want is BEING free. unidiomatic

The reason the ing-forms do not work here, I believe, is that this syntactic pattern is elliptical, and the ing-form of the verb is not a valid complement for the verbs WANT and CAN.

All you can do is, [you can] wait.

All you can do is, [you can] waiting. no

What we want is, [we want] to be free.

What we want is, [we want] being free. no

  • Alright, thanks for the answer. Then, I guess we are in a sort of blurred area when it comes to the verb "to be" + ing form or infinitives. Based on your answer, I could simply rephrase the sentences this way: "Your only option is waiting (for the results)" and "Our strongest desire is being free". I don't know if those'd sound odd to a native speaker's ear, but I'm pretty sure they are not ungrammatical. Bottom line: it is the context (like the use of the verbs "can" or "want") that somehow decides what should follow the verb "to be' (either an infinitive or -ing form). Do you agree?
    – Pehnt
    Commented Jan 13, 2019 at 14:13
  • Yes. Those are grammatical. But I wouldn't call it a "gray area" relating to the verb-to-be. The syntax of the examples in your question and the syntax of these sentences in your comment is quite different. In the OP the subject of is is a clause (all you can do and what we want) whereas in the sentences in your comment, the subject of is is a simple noun phrase.
    – TimR
    Commented Jan 13, 2019 at 14:17

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