The sentence

‘If I had been you/If I had been in your position’
We often use If I had been you and If I had been in your position to describe what we
would have done I someone else’s position
If I had been you/If I had been in your position. I would have accepted their offer.
‘If’ + past perfect + modal: ‘If he had known the facts, he might have …’
When we use would have in the main clause, we are expressing as much certainly as
possible:
If he had known the facts, he would have told us what to do. (certain or nearly certain)
if we don’t feel ‘certain’ enough to use would have, we can use another modal to say what
would have been possible:
if he had known the facts, he might have told us what to do. (it’s possible)
if he had known the facts, he could have told us what to do. (he would have been able)
D. Mixed conditionals; ‘unless/if … not’, etc.
Mixed tenses in conditional sentences
We do not always have to stick rigidly to the ‘three types of conditional sentences’. There
are occasions when we can use any tenses in if-clauses, depending on the context:
If I am as clever as you say I am, I would have been rich by now. Type 1 + Type 3
If you knew me better, you wouldn’t have said that. Type 2 + Type 3
If I had had your advantages, I’d be better off now. Type 3 + Type 2
‘If not’ and ‘unless’
1. We can use if … not and unless in place of each other when we are saying ‘except if’.
Unless is ‘stronger’ than if not and we sometimes use it in ‘threats’:
If you don’t change your mind I won’t be able to help you. (= Except if you change …)
Unless you change your mind, I won’t be able to help you (= Except if you change …)
2. We cannot use unless in place of if not when if not doesn’t mean ‘except it’:
I’ll be surprised if he doesn’t win. (if not doesn’t mean ‘except if’)
She’d be better company if she didn’t complain so much. (if not doesn’t mean ‘except if’)
3. We often use unless (never if … not) to introduce and afterthought:
I couldn’t have got to the meeting – unless, of course, I had caught an earlier train.
Conjunctions we can sometimes use in place of ‘If’
We can introduce conditionals with conjunctions which do not always have exactly the
same meaning as if, for example: assuming (that), even if, on (the) condition (that), provided
(or providing) that, so long as, suppose and supposing:
Assuming (that) it’s fine tomorrow, we’ll go for a swim.
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