Most people say I wish I could, I wish you would.

Can we use I wish I can, I wish you will?

I'd like to know what the main differences between the usage of can/will and could/would are when wishing.

Is it related to the subjunctive? Because one says “I wish I were”, not “I wish I am”, so are would and could the subjunctive forms of can and will?

Or is it something else entirely?

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    It may be influenced by the specific verb. I've never heard "I wish you will..." or "I wish I can...," but "I hope you will..." and "I hope I can..." sound fine. – vpn Oct 26 '16 at 3:00

OK, piece by piece.

Most people say I wish I could, I wish you would.
Can we use I wish I can, I wish you will?

No. *I wish I can and *I wish you will are both ungrammatical sentences. As pointed out.

I'd like to know what the main differences are between the usage of can/will and could/would when wishing.

Simple enough. It's the interaction of two syntactic and semantic phenomena:

1. The presupposition of a counterfactual complement for the English verb wish

2. The various senses of the modal auxiliaries can, could, will, and would.

The first one means that part of the meaning of wish is that its direct object must not be true; one can't wish to own something one already owns, for instance. Wishes require counterfactual (aka irrealis) complements. That's why they're linked up with negatives so often.

All predicates have specific subcategorizations like this; requirements for its subject, object, and context. It's part of the meaning of a predicate. Wish, for instance, can take a tensed complement clause, though the that complementizer is often omitted, especially in short or fixed phrases.

A that-complement of wish indicates its counterfactual nature by using a past tense form when referring to the present time

  • I wish that they were not in this room.
  • I wish they weren't here.

and a past perfect construction when referring to a past time

  • I wish that I had not seen the accident.
  • I wish I hadn't seen it.

Wish can also take an infinitive complement with A-Equi. This is a very formal construction, and can only occur with a future event.

  • I wish to ride in the first class compartment.

But those are the only complement clause types that wish can take; embedded questions and gerund clauses are ungrammatical with wish

  • *I wish what I had(n't) seen.
  • *I wish (my) (not) having seen it

The other interaction is from various senses of these four modal auxiliaries. All modals, including modal auxiliary verbs, have irregular syntax, ambiguous semantics, and arbitrary pragmatics.

In particular, will, would, can, and could all have multiple meanings. One type that they share in pairs is root variation: can alternates with could, and will alternates with would.

Historically, this is because in Old and Middle English (as in Modern German), modal auxiliary verbs were inflected, and had present, past, infinitive, and participle forms, unlike modern English modal auxiliaries, which are completely defective and only occur as auxiliary verbs.

In this case, will comes from the present tense form and would from the past; ditto can (originally present) and could (originally past). Most of the time, there is nothing "past" about could or would. On the contrary, they usually refer to something in the future (which is also "irrealis", since it's not real yet), rather than the past. But this old "past" sense still shows up with certain constructions, for instance:

  • When I was young, I could do 100 pullups, but now I can only do 90.
  • When I saw them, they would cook three meals a day, but now they'll very seldom cook.

And they can, in certain contexts, refer to a past that never occurred. And, as it turns out, the complement clause of wish is one of those certain contexts in which the "past" sense of would and could comes in handy to signal the irrealis status of the complement of wish.


Is it related to the subjunctive? Because one says "I wish I were", not "I wish I am", so are would and could the subjunctive forms of can and will?

It's distantly related to the subjunctive. About second-cousin-once-removed distantly related. There's something like it in the German subjunctive, but German has inflected modals and supports a full assembly of subjunctive verb forms for every verb, while no English verb has a specifically subjunctive verb form; nor are there any subjunctive mood paradigms.

Giving the intersection of two rules a name you're not sure of yourself won't really explain anything, so don't worry about "subjunctive". Think of this as one more little foothold on our way up the syntactic mountain.

  • I think your answer is great except that you are denying "I wish that construction" is the subjunctive. I also can't believe some grammarians would say could can function only as a modal while acknowledging it expresses the past tense of can. I see some contradiction or conspiracy theory here and wonder what difference would it make if you say "I wish that construction" is nothing but the subjunctive. – user140086 Oct 30 '16 at 17:10
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    @Rathony: Could is a modal; and it functions as a modal in all its uses. It can only appear as the first auxiliary verb in finite clauses, and it must be followed by an infinitive verb form. That's the definition of "English modal auxiliary verb". Same as can, shall, should, will, would, may, might, must, and sometimes need and dare. Saying it's "subjunctive" adds nothing to the description. Unless you have a formal definition of "subjunctive" that predicts all those modal properties, which I would be interested in seeing. – John Lawler Oct 30 '16 at 18:20
  • I am not denying could is a modal. I am just saying it is a two-faced verb that can function in two ways, i.e., the past form of can (closer to an auxiliary than a modal) and a modal verb (that can't inflect). Don't you think it is a bit weird to say "If I were a bird, I could fly away" is the subjunctive and "I wish I could fly away" is not the subjunctive, but its relative of the subjunctive? I don't really get it. – user140086 Oct 30 '16 at 18:29
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    You're using very confusing terminology, so I can't understand your objection. Modal auxiliary verbs are not "closer to an auxiliary"; they are auxiliaries. The'yre modals, too; that's why they're called "modal auxiliaries". As I explained, could comes historically from the past form of the earlier inflected modal. These past forms have been reified as untensed modal auxiliaries in modern English, but their old past sense occurs in a couple of minor constructions, like the irrealis complement of wish. Don't worry about what I think is weird; what do you think "subjunctive" means? – John Lawler Oct 30 '16 at 20:21
  • That's what "subjunctive" means? Then it's not a grammatical term; certainly not a "subjunctive mood" in English. Grammar isn't about meaning; it's about constructions. "a past that never occurred" is an example of irrealis, not "subjunctive". What Huddleston & Pullum call "subjunctive" is the use of an infinitive form of the verb instead of a present form in a that-clause complement of impositive verbs; e.g, It's important that he be on time tomorrow. The counterfactual marked by past in the complement of wish they call "irrealis", not "subjunctive". – John Lawler Oct 31 '16 at 15:04

In this context, could and would are used to express an hypothetical scenario. Can and will in contrast have a sense of immediacy and certainty, so it wouldn't fit.


"Can" asks the possibility, as in "Can you help me?". "Would" asks the person addressed if they have the will, as in "Would you help me?"

So "would" or "will" is more polite, implying that the person addressed has a choice to act.

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