Unit 37 If I do... and If I did...

We use ‘If I + present simple..., I + future simple’ when is a real possibility that something will happen.

Sue has lost her watch. She thinks it may be at Ann’s house. Sue: I think I left my watch at your house. Have you seen it. Ann: No, but I’ll have a look when I get home. If I find it, I’ll tell you.

We use ‘If I + past simple..., I’d (= I would) ... (not ‘If I + present simple..., I’ll...’) when we aren’t thinking about a real possibility, we are imagining the situation and don’t really expect this to happen. We use past, but the meaning is not past.

Ann says: If I found a wallet in the street, I’d take it to the police. What would you do if you won a million pounds? I don’t really want to go their party, but I probably will go. They’d be offended if I didn’t go.

We do not normally use would in the if-part of the sentence: I’d be very frightened if somebody pointed a gun at me. (not ‘if somebody would point’) If I didn’t go their party, they’d be offended. (not ‘If I wouldn’t go’)

But it is possible to say ‘if... would’ when you ask somebody to do something: (form a formal letter) I would be grateful if you would send me your brochure as soon as possible. ‘Shall I close the door?’ ‘Yes, please, if you would.’

In the other past of the sentence (not the if-part) we use would (‘d)/wouldn’t): If you took more exercise, you’d (= you would) probably feel healthier. Would you mind if I used your phone?

Could and might are also possible: If you took more exercise, you might feel healthier. (= it is possible that you would feel healthier). If it stopped raining, we could go out. (= we would be able to go out)