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All the textbooks I have ever come across during the course of my studying English emphasize that future tense should not be used in conditional clauses.

For example,

If it rains in the evening, we will not go for a walk. (if it will rain in the evening...)

We decided to go for a walk if it didn't rain in the evening. (...if it wouldn't rain in the evening)

However, in the following sentence I'm really inclined to use the future tense.

Don't implement this feature if it will significantly increase the complexity of the user interface.

According to all the rules I know of, the future tense is illegal here. However, my gut feeling tells me that the sentence is correct. If I am wrong, the question ends here. Otherwise please read on. I find the last example different from my first two because:

  • In the first examples we must wait and see if the condition is true, and then make a decision accordingly, whereas in the last example, we must actually analyze/predict/forecast the future in order to make the decision in the present.
  • (might be irrelevant) In my first language - Armenian - where we have a special mood for conditions, the translation of the third sentence actually uses indicative, whereas the first two use that special mood (the conditional mood, as it were).

Since the second would-be principle is easier for me to experiment with, I noticed that every time a condition uses the indicative mood in my language, I'm inclined to use the future tense in English. As another example:

I will give you the money if it will make you happier.

Am I imagining things or are my examples of the future tense in the conditional clause valid? If they are valid, what rule would you suggest to distinguish the cases when it's OK? (I do realize that translating a sentence to another language and analyzing the translation doesn't really count as a rule).

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At first glance, your intuitive choice seems misplaced as far as the English language is concerned. As in Armenian, so it is in at least some other languages, but not in English I am afraid. By the very sound of it (possibly because it's atypical), the future tense stands out as odd. Let's see what theoretical explanations the others may provide. –  Kris Feb 3 '12 at 14:41
@Kitḫ: I haven't looked at the reference, but Armen's questions don't concern the subjunctive. –  Barrie England Feb 3 '12 at 16:03
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5 Answers

up vote 6 down vote accepted

I think the difference between the two types of examples that you've exhibited is the relative placement in time of the action in the "if" clause, and the action in the other clause.

  • If it rains in the evening, we won't go for a walk - here, the event of raining occurs BEFORE the decision about whether to go for a walk.
  • My teeth will rot if I eat too much sugar - presumably, I'll be eating the sugar BEFORE my teeth rot.
  • If it will significantly increase complexity, don't implement this feature - here, the increasing of complexity occurs AFTER the implementation of the feature.
  • I will give you money if it will make you happier - here, you becoming happier occurs AFTER I give you the money.

In all the cases where the "if" part happens first chronologically, we use the present tense. In the cases where the "if" part happens second, we use the future tense. However, because sentences of the first type are far more common than sentences in the second type, a good rule for learners to adopt is "don't use the future tense with IF".

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And to complicate things further, there are two cases when the "if" part happens second chronologically: the case where it is a consequence of the action in the main clause, and the case where it is simply a prediction of an event. In the second case, I think we have to put it into the future using "going to". In the first case, we can use "will". An example of the second case is "if it's going to rain later, I'll bring my umbrella." –  Peter Shor Feb 4 '12 at 2:42
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In some cases, it is possible to use "will" in "if" sentences to imply

A) willingness

If you'll just hold the door open for me a moment, I can take this table out to the kitchen.

B) obstinate persistence

If you will keep all the windows shut, of course you'll get headaches

C) if the "if" action is after the main action, will (or an equivalent expression indicating the Future) is used in the if clause

If aspirins will cure it, I'll take a couple tonight.

Please check Wikipedia and lingua.org and a page from Berkeley

Edit 1 Per @Brett Reynolds and @Peter Shor

As far as I can see, "will" may first impose a change in the order of actions and then "both "will" and "order of action" contribute to meaning. The contribution depends on context and may imply "a willingness", "a persistence" "a wish", "a prediction" e.t.c. Please compare:

I will give money if you will do it.

I will give money if you do it.

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Good points. Is it a coincidence that your examples all start with the condition? –  GertArnold Feb 3 '12 at 19:19
+1 Your C) point is actually what I was referring to! –  Armen Ծիրունյան Feb 3 '12 at 22:02
I'm afraid, c) is wrong. The order has nothing to do with it. Consider, *if it will rain later, I'll bring my umbrella. –  Brett Reynolds Feb 4 '12 at 1:45
@Brett: the order certainly has something to do with the tense you use. You shouldn't say "if it rains later, I'll bring my umbrella". You'd say "if it's going to rain later", the other future verb construction in English. –  Peter Shor Feb 4 '12 at 2:25
I believe that the rule for case c) is that when the "if" clause is a prediction, you must use "going to", but when the "if" clause is a consequence of the action in the main clause, you can use "will" –  Peter Shor Feb 4 '12 at 2:36
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The first thing to say is that English has no future tense. (This sometimes comes as a surprise.) There are, however, various ways of expressing the future and will + the plain form of the main verb is one of them.

It’s true that that construction is not found in the if clause of conditional sentences such as your first example (‘If it rains in the evening . . .’). However, there are occasions when it is used, particularly where will expresses volition, as in ‘If you will follow me, I’ll take you to your table.’ That could be expressed as ‘If you follow me, . . .’, but the construction with will adds a degree of politeness. Your example ‘I will give you the money if it will make you happier’ is similar. That could also be expressed as ‘. . . if it makes you happier’, but here the will construction softens what might otherwise be a harsh remark. It assumes (or, for the sake of kindness, appears to assume) a greater probability that the condition will be met.

Much the same applies in your example ‘Don't implement this feature if it will significantly increase the complexity of the user interface.’ It, too, could be written with ‘. . . if it significantly increases . . .’ By using the will construction, however, the writer to some extent prejudges the chance that the complexity of the interface will be increased if the instruction is ignored.

The authors of the ‘Cambridge Grammar of English' sum up these constructions when they write:

Modal verbs (most typically will or would) may occur in conditional clauses if they have a meaning of willingness or prediction, or where it is important to mark politeness.

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I think CGE is mistaken when it allows modals for prediction in if clauses. It's actually disastrously chalk full of errors. english-jack.blogspot.com/2008/03/more-muddled-grammar.html –  Brett Reynolds Feb 3 '12 at 16:23
@BrettReynolds, can you explicate "chalk full"? –  jwpat7 Feb 3 '12 at 17:05
Slip o' the fingers. "Chalk full" should be "chock full" = very full. –  Brett Reynolds Feb 3 '12 at 17:23
@BrettReynolds: I hadn’t previously seen the Huddleston review, but his criticisms must of course be taken seriously. I don’t use it all that much, partly because I haven’t found it particularly user-friendly, and that applies not only to the index. For the case in hand, the willingness and politeness points hold, even if the prediction one doesn’t. But we still have to explain to Armen how ‘if it will significantly increase’ differs from ‘if it significantly increases’. –  Barrie England Feb 3 '12 at 17:28
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Your intuition is correct and the "rule" is the problem. The misunderstanding arises partially, at least, from the idea English even has a future tense. It doesn't. What it does have, however, is modal auxiliary verbs like will, may, and can, which typically have future time reference.

In fact, the problem only resides with certain modals (mainly will, may, might, and could) when they are used to express probability. Thus, it could rain tomorrow doesn't work as *if it could rain tomorrow, but you could help me tomorrow, couldn't you easily becomes if you could help me tomorrow because could here is denoting ability or willingness rather than probability. Note that this also holds true for present and past time as well as future time.

In if it will make you happier, the speaker is not predicting that it will make you happier. That is taken for granted. That's why you can respond "It does/will. It makes/will make me happier."

Similarly, if it will significantly increase the complexity of the user interface does not involve a prediction. Unlike in the case of rain, where it is simply impossible for anybody to know, here it is merely unknown to the person giving the advice, but it is taken for granted that the receiver of that advice knows the effect that "it" will have.

This also, by the way, explains why the so-called "going-to future" isn't a problem. I discuss this point here.

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Some explanations for the multiple down votes would be appreciated. –  Brett Reynolds Feb 4 '12 at 13:23
I didn't downvote, but I found your explanation written very confusingly. –  Peter Shor Feb 4 '12 at 14:27
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You can use will in the if-clause if you are focused on the result. Consider:

  • I will give you the money if it will make you happier.
  • I will give you the money if you ask nicely.

In sentence one the result of giving is making your friend happy. In sentence two the condition of giving is that your friend asks nicely.

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But what is the difference between 'I will give you the money if it will make you happier' and 'I will give you the money if it makes you happier'? –  Barrie England Feb 4 '12 at 12:35
My post was an attempt to give a simplistic explanation of when it is possible to break what the OP thought was a rule that if clauses cannot contain will. But as your question makes clear, the will is not mandatory in result clauses. It could be that I will give you the money if it makes you happier implies that the being happier will occur now, on me telling you this. And I will give you the money if it will make you happier implies the being happier will occur when you receive the money. But I'm not ready to go to the barricades in support of this suggestion. –  Shoe Feb 4 '12 at 13:39
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