Suggestions

We use suppose, supposing and what if + present verb form to make suggestions about what might happen:

A: What time shall we meet?

B: Suppose we meet in the offices downstairs at four o’clock?

A:That’s perfect. I’ll let the others know.

Supposing I don’t bring my car and you and I travel together. That would save us half the cost of petrol and parking.

A: The electricity has gone. There must be a power cut.

B: What if we find the candles and put them around the room?

A: Okay. Good idea. Do you know where they are?

Possibility

When we are less certain, we use suppose, supposing and what if + past form to talk about future possibility:

Suppose we asked Mary to baby-sit? Do you think she’d do it? (not as certain as Suppose we ask Mary to baby-sit?)

Supposing someone else wrote the essay. How would we know? (not as certain as Supposing someone else writes the essay …)

A: What if I gave up working full-time. I’d love that.

B: You’re joking surely!!

When we refer to something that did not happen (something hypothetical), we use the past perfect:

Suppose we hadn’t brought our umbrellas. (We did bring our umbrellas.)

Supposing they had closed the road. Would that have been a good idea? (They didn’t close the road.)

What if I had accidentally told Maria about the party! That would have ruined the surprise. (I didn’t tell Maria about the party.)

Warning:

We use be supposed to to talk about obligations and arrangements, not suggestions.

You are supposed to put money in the parking meter!