[bravejason]

In some competitive auctions, responder’s pass shows a hand that is strong (or not weak) whereas responder’s double shows a weak hand. Does anyone know why it is this way as opposed to the other way around? I know the other way around is played, but standard or more common method seems to be that pass=strong and double=weak. I’m looking for history lesson more than anything else, but would also be curious to know the pros/cons of each.

[mycroft]

This kind of thing (commonly known as "forcing pass situations", as opposed to "weak opening" bidding systems (don't worry about them, but they're also frequently known as "forcing pass". Not what we mean here)) does the same thing that transfer auctions do - increase the different kinds of hands we can show.

Partnerships need to define what constitutes a forcing auction (and to what levels), at which point if you double for a strong hand, partner has to decide what to do with a "strong hand". In fact, most commonly, the strong hand does not want to defend, they want to bid more; so partner would normally pull the double. By inverting this, passing with stuff and no general direction, doubling as a "beware going on" signal, and bidding directly as "beware defending" signal, you then also let partner decide on the "no general direction". You *also* get "pass-and-pull" auctions, initially saying "I don't know what to do, you decide", then overriding the decision to defend to say something else (generally this is also very strong, not for bridge theoretic reasons, but for Law reasons; pulling a slow double with a non-obvious hand will get a director call and will be rolled back).

This most easily is seen in game-forcing auctions when they interfere. Now, you want to get where you want to go, but also to decide to defend if it looks like a better or safer score. You have decided (somehow) that you will not let them play undoubled with the strength you have. So, now, you can bid to say you have offensive values, double to say your values are more defensive (or you see too many losers for the 5-level, for instance), or pass with either a "I can't decide, you pick" or "I have serious extra values, partner, and they've given us a chance to show them" (where you override partner's decision).

Another meta-agreement some pairs have is "when forced to some contract, bidding that contract is the absolute weakest option"; both pass and double show at least some additional.
1♠-(2♦)-3♦-(X), for instance, 3♠ (what partner's "strong raise" cuebid" forced us to) says "my opener is really minimum", pass shows something (and extras), as does XX and 3♥. (Side note: this is why you shouldn't routinely double their cue-bids as "liking our suit". You don't want to give them 3 calls below 3♠ when before they had 1! In fact, many people invert pass and double here as well (provided partner has enough cards that they won't try to play the cuebid!) - double *discourages* diamonds, pass is neutral+.)

Sometimes people are playing something other than natural, and they call this "pass-double inversion" - where pass explicitly means "I want to defend" and double means "I want to go on, but I'm doubling in case you are the one wanting to defend". I actually play that when I preempt and they bid game (my double can't be "I can set this", so it's "I want to sacrifice, but just in case you can set this..."). That's not necessarily "pass=strong, double=weak", though.

Remember there are also "blackwood interference systems" where pass (and double) have specific meanings (not necessarily "strong" or "weak").

So my short answer is "because it's more flexible and easier to do it that way".

[bravejason]

Thanks. That was very educational. I hadn’t thought about it as a forcing pass concept.

[blackshoe]

Very good article, Mycroft.