[barmar]

gordontd, on 2018-August-24, 02:55, said:

I think there is some confusion in this thread about the question of UI. West's opening bid out of turn is UI to East. However, once East has opened, if West has a comparable bid available and selects it, then the question of UI does not arise.

I think that's why the meaning of a CC is required to be a subset of the original call, and not the other way around.

Consider the situation in the OP. The original call shows at least opening values. If the replacement is a 1{SP] response and opener jumps to game, he's clearly taking advantage of knowing that partner originally tried to open, which is supposed to be UI.

That's why a 1♠ response is not within the definition of a CC.

[barmar]

blackshoe, on 2018-August-23, 19:17, said:

How do you know this? The law doesn't say so.

The law uses "meaning" for the first two cases, and "purpose" for the last. I interpret this change in wording to distinguish calls that show something (e.g. hand strength, suit lengths, location of controls) from calls that do something. Also, notice the examples given of the types of purposes intended: "e.g. an asking bid or a relay".

Admittedly, the distinction is fuzzy. If a call shows something, its purpose is to show that. But it seems clear to me that the Law was written this way to address artificial asking bids differently from bids that show something.

Note, that I'm not saying that the first two categories are only for natural bids. Jacoby 2NT is an artificial bid that shows something, so if you had to replace it you'd need to find a bid that shows something similar.

Are there natural asking bids or relays? I suppose nothing precludes them. If a bid is natural and forcing, its purpose might be to get partner to further describe his hand.