This is what my wife said to me this morning: "But we can't not go" meaning
(more or less) 'we have to go' I had just been thinking of Larry's list of
examples including:
You can not go to the party. (it's up to you)
You {cannot/can't} go to the party. (sorry about that)
I don't think anyone could say *But we cannot not go."
Dale Coye
Wilton, NH