# Using 'doubt' with 'could' or 'will'

I have to solve the following exercise from "Grammar and vocabulary for Cambridge advance and proficiency" Pag 51 number 4. Specifically I have to complete a sentence so that it has a similar meaning to the first sentence, using the word given. I have to use from 2 to 8 words.

The original sentence is:

I wouldn't have thought there's much chance of that package being here before Friday.

The word given is doubt

The sentence to be filled is

I ..... here before Friday.

This is my solution:

I doubt the package could be here before Friday

However, the book gives me the following one:

I doubt the package will be here before Friday.

At this point I have one questions:

Is the sentence of mine wrong? why?

• I think your answer was a good one; you are doubting the possibility ('much chance') of the package arriving by Friday. So 'could' is OK, I feel. Who created and published the book you mentioned? Commented Apr 25, 2023 at 14:39
• Longman. Richard Side and Guy Wellman Commented Apr 25, 2023 at 14:57
• I would say "the package could {make it/get} here" or "the package will {be/get/make it} here". For some reason my AmE ear doesn't like "doubt" with "be here" with "could". I wouldn't go so far as to say it's wrong, because I don't know exactly why I prefer will. Commented Apr 25, 2023 at 15:45
• @ColleenV - Would you object to When René Descartes (1596-1650) first proposed his Cartesian or analytic geometry, I doubt that he could have foreseen what a revolution it would generate? Commented Apr 25, 2023 at 17:42
• @MichaelHarvey Nope. It's something about doubting the x could BE here, not all uses of could with doubt. "I doubt the agent could be fast enough to deliver it by Friday" also seems fine. "The package could be hidden on the porch, but I doubt it" is also fine. "I doubt the package could be hidden on the porch... it's too big" is ok too. weird. Commented Apr 25, 2023 at 17:46

Short answer: I think your sentence is fine and should have been marked correct.

Longer answer: There are subtle and complicated differences in meaning.

In general, the difference between "could" and "will" is a chance versus a certainty. If you said, "The package will arrive tomorrow", you are saying that it is a certainty that this will happen. "The package could arrive tomorrow" says that it might, but then again it might not.

Add the word "doubt" to the sentence and things get more complicated. If you say that you "doubt it could", then you are saying that it is not possible. Could it happen? Is it possible that it will happen? You don't think so. The idea that it will arrive by Friday is simply impossible.

"Doubt it will" is saying that you don't think it will actually happen. It is possible, but unlikely.

That is, "doubt it could" means you don't think it's even possible. "Doubt it will" means it may be possible but you don't think it is likely.

Arguably, the original sentence is saying that it is possible but unlikely. So "doubt it will" is probably closer in meaning.

But it is such a fine distinction, if I was grading the test I would have marked it right.