"If he were to do" vs. "if he did"

Question

What is the difference in the meaning of following sentences?

1. If Tom were to do my homework, I would watch a film.

2. If Tom did my homework, I would watch a film.

I know that both of these questions express unlikely or imagined condition. I'm not sure but I think. There's is difference in the meaning between two sentences. Here is my opinion:

1. In the first sentence, the speaker thinks that it's impossible for Tom to do his homework or Tom isn't able to do his homework or Tom is a baby. So, the speaker is imagining a impossible thing.

2. In the second sentence, the speaker thinks it's a bit possible for Tom to do his homework.Tom is the speaker's friend and Tom is able to his homework but he isn't willing to do. So, the speaker is expressing his imagination and saying "If Tom did my homework I'd watch a film".

For more clearification of my openion i would say: I'm not sure but I'm just guessing the possible meaning of those sentences like this:

both sentences are all about imagination but first sentence indicates impossible imagination and second expresses unlikely but expected imagination. AM i correct?

Am I correct in my opinion ? If not, what is the correct meaning? Please explain it in details.

Answer 1

There is little or no difference in meaning between the two sentences. There is a tiny difference in emphasis, which is hard to explain. It has to do with the way you clarify or remove ambiguity in English by adding redundancy, also illustrated here.

Hypothetical possibility with present tense

In both sentences, "his doing my homework" is a hypothetical possibility. A consequence of that possibility, indicated by would, is that the speaker would watch a film.

English provides a variety of ways to indicate a hypothetical possibility. The simplest is just to precede the clause describing the possibility with the word if. You could say:

If he does my homework, I would watch a film.

However, in this form, the meaning of the present tense is not clear. Does it mean "right now"? No, that's not how the present tense is normally used in English. Does it mean "in general"—that is, "if he often, frequently, usually does my homework…" or "if it is his responsibility to do my homework…"? This is how the present tense is most commonly used in English, but it's probably not the intended meaning in this sentence, since "I would watch a film" suggests that the speaker is talking about only one occasion. However, would can also mean a habitual, recurring action. The little English grammatical words tend to be very ambiguous!

So, in English, we often add clarity by repeating or echoing the same meaning in multiple ways. This helps reduce the ambiguity of each individual word or grammatical choice, especially regarding what the speaker means about the time of an event, whether the event is real or hypothetical, what the consequence is and when it occurs, whether the hypothesis is normal or unusual or an offer in a negotiation, etc.

Past tense to indicate future possibility

To avoid the ambiguity described above, it's common in English to describe a hypothetical future possibility by putting it into the past tense, like this:

If he did my homework, I would watch a film.

Another typical example:

If you visited me next July, we could watch the fireworks together.

You might think that using the past tense to indicate a hypothetical future possibility is ripe for confusion, and you would be right. For example, "If he did my homework, I would watch a film" could also mean a past possibility and a present consequence: if he already finished doing my homework, then I would watch a film right now.

So, when using the past tense to indicate a future possibility, people often add additional words to reinforce the interpretation that the sentence is about the future. For example, the sentence with "visited" has the adverbial phrase "next July", which makes fully clear that that the sentence is about a future possibility.

Subjunctive mood

The sentence about homework does not have an adverbial phrase to make the time explicit. So, to be perfectly clear that you are using the past tense for a future possibility, you might use the subjunctive mood. The subjunctive mood means hypothetical possibility! The subjunctive mood is rare in English, and often the form of the verb doesn't unambiguously indicate the subjunctive mood, but with the verb "to be" and subject "I", the subjunctive mood is completely unambiguous, since "were" can't make grammatical sense in any other interpretation:

If he were to do my homework, I would watch a film.

Infinitive verb form

The reason for the infinitive to do is because the infinitive form of a verb avoids attaching it to a particular time. (For more about that, see this answer.) The past subjunctive were, combined with if, adds somewhat more redundancy to indicate that the sentence is talking about a hypothetical future possibility and its consequence.

Conclusion

Because the sentence talks about homework and watching a film, it sounds like the speaker is referring to hypothetical events that would occur this evening. So, you don't really need the subjunctive mood to be clear about what time is being talked about. The sentence with did is clear enough.

Using the infinitive to do instead of the finite did creates a slightly more abstracted feeling about the possibility. Using the past subjunctive were where it's not necessary adds to that feeling of abstract possibility. As I said, the difference in meaning is just a tiny shade of emphasis. But you can learn a lot about English grammar by understanding why the switch from did to were to do creates that tiny shade of difference!

Answer 2

Both the sentences are conditional type 2, indicative of a hypothetical or contrafactual situation in the present or future.. In other words, in both the sentences, the if-clause takes the past subjunctive. However, the meaning of were + to do is ambiguous; it's used to convey different senses. For example:

If he were to do my homework = If he did my homework, if he intended to do my homework, or if he were supposed/expected/directed/instructed/obliged to do my homework.

I think because of the ambiguity of the subjunctive were to do, the use of the past tense did is more common to express the same meaning of doing something in the present or future.

Answer 3

They're both in the subjunctive mood. The first one is sometimes called the "future subjunctive" in English and the second one is usually called the past subjunctive:

1. "If Tom were to do my homework, I would watch a film."

("were to do" is the future subjunctive of the verb "to do")

2. "If Tom did my homework, I would watch a film."

("did" is the past subjunctive of the verb "to do")

I am probably going to get some flak from the modern grammarians on this forum for my use of terms like "past subjunctive" for "did" in no. 2 and God forbid I even utter the term "future subjunctive" because many modern grammarians don't believe that English has a "future indicative" let alone a "future subjunctive", but guess what, boys? I just uttered it. Now, I shall start with the ever-so-slight difference between the two statements at hand:

1. "If Tom were to do my homework, I would watch a film."

2. "If Tom did my homework, I would watch a film."

No. 1 uses the future subjunctive of the verb "to do". The future subjunctive is very formal and the rule for it has exceptions, so what I tell you here is going to be how it's used 99% of the time rather than all of the time. For the other 1%, it is used politely to talk about a condition in the future, whether that condition be counterfactual or not. Anyway, the future subjunctive appears a lot in formal English essays, papers, or dissertations, but it is heard in conversation here and there as well. It is used to talk about an event in the future that is "very" unlikely, if not impossible, to occur.

Unlike No. 2, which uses the past subjunctive, No. 1 could be talking about a condition that is counterfactual in the distant future; no. 2 does not talk about the distant future; no. 2 is using the past subjunctive, which talks about a condition that is counterfactual either in the present or near future. For instance:

"If I were to visit the planet Pluto, I would pack a lot of warm clothes."

In my imaginary world, one day I shall visit Pluto and I will have to pack warm clothes.

"If I were to be crowned King of England, I would rule with an iron fist."

In my imaginary world, one day I shall be crowned king and I will rule with an iron fist.

"If one were to look closely at the two examples above, he could easily see the subtlety of the future subjunctive."

Remember that 1% I told you about; here it is. This is an example of politeness using the future subjunctive and it is often found in formal essays and papers. I have written this before in many formal essays in high school and college over the years. I am politely trying to direct the reader's attention to something. It's more polite than the imperative,

"Look closely at the two examples."

If I were to have used the past subjunctive "looked" in the situation above, it wouldn't sound so polite as it does with the future subjunctive (This is an example of the future perfect subjunctive, which expresses courteousness herein). Usually, we use the past subjunctive in counterfactual conditions, but it can be used for politeness in some cases like the future subjunctive; however, the future subjunctive is far more polite and its meaning is clearer. For instance, last week, my grandfather and I were talking about his getting eye surgery to correct his blindness in his one bad eye and I said,

"That would be great if you had your sight back."

(past subjunctive use of politeness)

However, I could have said this a nimiety of ways:

"That would be great if you [should] have your sight back."

(A mixture of past subjunctive "would" with present subjunctive "[should] have": a little less polite than the above one)

"That will be great if you [should] have your sight back."

(archaic present subjunctive: not so polite [it could read "if he have"])

"That would be great if you were to have your sight back."

(future subjunctive: very polite)

We know that "were + infinitive" equals the future subjunctive because there is no present subjunctive possibility; that is, one cannot say or write "be + infinitive".

Here's a paradigm of the verb "to be" in the subjunctive so that you can see some of the different forms although I don't list every possible schema because passive voices in the subjunctive are possible in some instances, not to mention continuous constructions.

"If that be the case, I shall eat my hat."

"Be that the case, I shall eat my hat."

(present subjunctive [archaic]: Modern English "is" or "should be" [inversion used in second example])

"If that should be the case, I shall eat my hat."

"Should that be the case, I shall eat my hat."

(present subjunctive replaced by using "should" before the verb [inversion used in second example])

"If that were the case, I should eat my hat."

"Were that the case, I should eat my hat."

(past subjunctive [inversion used in second example])

"If that were to be the case, I should eat my hat."

"Were that to be the case, I should eat my hat."

(future subjunctive [inversion used in second example])

"If that had been the case, I should have eaten my hat."

"Had that been the case, I should have eaten my hat."

(past perfect subjunctive [inversion used in second example])

It is essential that that have been the case at some point.

(present perfect subjunctive: [I show it like this because it is so rare in "if clauses" even in archaic English])

"If that were to have been the case, I should have eaten my hat."

"Were that to have been the case, I should have eaten my hat."

(future perfect subjunctive: [equivalent to the past perfect subjunctive in meaning, but more emphasis on the counterfactual reality of the past situation; inversion used in second example])

I hope that might have helped out those who have been struggling with this difficult concept. In the end, there's very little difference between the future subjunctive and past subjunctive, especially in the original example above. In the original example above regarding Tom and his homework, I would say no. 1 is more unlikely or more polite, depending on the context clues, than no. 2 is.