Please consider the following line:

What can we do? We need an alternative. It * * * incorporate X and * * * offer Y.

Which of the following verbs and forms is correct?

  1. has to
  2. needs to
  3. must
  4. had to
  5. should
  6. would have to

Which is best? Note that this is a scientific text.

How do they differ in meaning? The intention is that 'the alternative' does not yet exist and will be hard to find, so it looks conditional-ish to me. I have the feeling that 6. is the best, but it is so verbose. Does another form express the same?

1 Answer 1


Firstly, I think 5 of the 6 listed options are grammatically correct to replace the * * * gaps in your quote. Only had to would look odd to me, as we're not talking in the past tense.

I don't see any grammatical issue with using any combination of the 5 valid options in either gap, but in my experience it would be most common usage to just place one of these options into the first gap only (referring to X), as the same will then be implied for Y as well:

What can we do? We need an alternative. It must incorporate X and must offer Y.

would usually be written or said as:

What can we do? We need an alternative. It must incorporate X and offer Y.

In the second quote above, it is implied that the alternative must offer Y.

I terms of meaning, I would say the following are all synonymous:

  1. has to
  2. needs to
  3. must

They all imply that the property being referred to (X or Y) is mandatory, so the alternative being considered is not an option unless it has those properties.

The option

  1. should

is much softer, with no direct implication that the requirement is mandatory, so it leaves open the possibility that viable alternatives could be found which do not incorporate X or offer Y.

I agree with you in your assessment that the best option is:

  1. would have to

This retains the mandatory nature of the first 3 options, but also has the connotation that you describe, that it might not be easy to find such an alternative. You could just as appropriately use would need to. It's the presence of the word would which makes these options sound more conditional.

So I would go with:

What can we do? We need an alternative. It would have to incorporate X and offer Y.

You can augment the questionability of the likelihood of finding such an alternative with something like:

What can we do? We need an alternative. It would have to incorporate X and also offer Y.


What can we do? We need an alternative. It would have to incorporate X while also also offer Y.

The latter option here implies that there is some conflict between being able to incorporate X while simultaneously offering Y.

  • Thanks for the detailed answer. (especially for ruling out 4. which was my secret fav) The repetition was intentional. I might also consider making it 2 or even 3 individual sentences just to emphasize the difficulty. Then a 3-fold repetition of 'would have to' seems pretty heavy. Are you saying, that the present tense is also OK/common or would it be perceived as slightly odd/basic by a native speaker?
    – old123987
    Dec 22, 2016 at 16:00
  • I think present tense is fine, just past tense that sounded odd to me.
    – 3N1GM4
    Dec 22, 2016 at 16:10
  • I included simple past in the list, because of the standard conditional clauses 'If I had A, I would do B'. The first part is the(a) condition(al), as it is in my example...
    – old123987
    Dec 23, 2016 at 10:33
  • I must admit, I am not sure on the technical definition of this construction, but as a native English speaker, it wouldn't make sense because you're saying "We need to find an alternative" as in, an alternative must be found in the future. Therefore, to follow up by stating properties that alternative must have had in the past doesn't make sense. I'm sure someone with the formal academic English skills to explain this can rephrase the point I'm making in the technically correct way.
    – 3N1GM4
    Dec 23, 2016 at 10:35
  • So for "had to" to make sense, I'd expect the whole sentence to be "What could we [have done]/[do]? We needed an alternative. It had to incorporate X and offer Y".
    – 3N1GM4
    Dec 23, 2016 at 10:37

You must log in to answer this question.

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