A practical english grammar - Vyssaja skola 1978
Clauses of condition
Sound symbols
These clauses are introduced by if, unless, as if, as though, and occasionally when. They are of two kinds: undetermined conditions (something that may be true, but of whose reality the speaker does not have certain knowledge; or something that is in the future), and unreal conditions (something that is hypothetical or contrary to fact, or at least is thought to be such by the speaker).
Undetermined conditions. The verb in undetermined if-clauses is in its ordinary form, except that future events are always referred to by the present tense. Will is never used in if-clauses except to mean “be willing.’’ In conditions having to do with habitual or customary actions, or with future events that are regarded as near-certainties, when can be used instead of if.
If I’m working I don’t like to be disturbed. (Habitually.) When I’m working I don’t like to be disturbed. (This sentence and the preceding one are equivalent.)
Give this message to John if you see him. (Your seeing him is uncertain.)
Give this message to John when you see him. (The speaker feels that the addressee is certain to see John.)
If it rains tomorrow, we will stay at home. (The speaker has no way of knowing what the future holds, and so uses if to state a possible real event of whose occurrence he can not be certain.)
Undetermined conditions in the past always indicate that the speaker does not know whether they occurred or not.
If he was there, I didn’t see him.
Will in if-clauses expresses willingness, not futurity.
If you will sign these papers, I won’t have to bother you further.
Should is used in if-clauses referring to future events to indicate that the speaker has little confidence that they will occur.
Please give John my best regards if you should see him. (I do not consider it very likely that you will see him.)
Unreal conditions. The verb in unreal if-clauses is always past tense (unreality being one of the meanings of the English “past” tense). The simple past tense expresses contemporary unreality; the past perfect expresses past unreality. The modals could and would when used in if-clauses usually have “unreal” meanings. If the verb in a contemporary unreal if-clause is be, the form were is used for all subjects. (The student will recall that the same rule applies to that-clauses after wish, which also express unreality.)
Contemporary unreality.
If my children spoke to me that way, I would be angry. (The fact is that they do not speak to me that way.)
If Mr. Evans were here, we could begin. (Mr. Evans is not here, and therefore we can not begin.)
If I had a car, I would drive to Mexico. (I do not have a car.) I would help you if I could. (I can not help you.)
You would like Chinese food if you would try it. (Would expresses willingness, and the speaker believes that the addressee is not willing to try Chinese food.)
Past unreality.
If I had had a car last summer, I would have driven to Mexico. If you had told me you were coming, I would have prepared dinner for you.
An elegant variation of the clause of past unreality omits if and begins the sentence with had.
Had we known what was about to happen, we would have acted differently.
A similar elegant variation of the if-clause with should referring to future events is also available.
Should you see him, please give him my regards.
Clauses with UNLESS. Clauses with if mean that the actual or supposed presence of the condition stated by the if-clause brings about the condition stated by the main clause. With unless-clauses, it is the absence of the condition that brings about the result stated by the main clause. Unless is generally restricted to use in expressing undetermined conditions.
He will be here by 8 o’clock unless he has car trouble on the way. (In the absence of his having car trouble, he will be here.)
Unless the weather was bad, my father always used to take a walk in the evening.
Clauses with AS IF. This conjunction, along with as though, which is equivalent to it in meaning, expresses unreality in contemporary situations. In past situations, it may express undetermined or unreal conditions.
He acts as if he were a millionaire. (He is not a millionaire.) British English is not nearly so insistent on the use of were in unreal clauses with as if as American English is, and consequently sentences such as “He acts as if he was a millionaire” can also be found in standard usage.
In the past, if the speaker knows the condition to be unreal, he ordinarily uses were instead of was (other forms of the past tense are the same for both undetermined and unreal conditions).
I felt as though I were (sometimes was) floating on a cloud.
It seemed as if I was being deceived. (I did not know whether I was being deceived or not; hence the condition is undetermined.)
Many English speakers use like instead of as if or as though, but this usage is so strongly condemned that it is avoided by all speakers who want to be judged correct. Learners of English may hear it occasionally, but they are warned not to imitate it.
He acts like he was a millionaire.