[kenrexford]

I thought of another example of the a posteriori being necessary.

Suppose you get what appears to be a passive club lead. Suppose a passive diamond lead is also possible. Suppose, however, that your club holding is solid (AKQJ combined, notrump contract).

A priori, you opponent could have held nothing in clubs or diamonds, or nothing in clubs but something in diamonds. He could not have something in clubs but nothing in diamonds. Thus, there are only two options.

However, only in the case of two nothings would he have flexibility.

If the eliminated option (nothing in diamonds but something in clubs) were available, then restricted choice suggests that the opponent lead from his only weakness, as 2/3 of the time he has strength in the other suit.

When that a priori analysis is not valid, because one of the 2/3 options is eliminated, a posteriori analysis still supports the restricted choice analysis, because the "both weak" option was flexible.

There could even be a one-suit or one-card restricted choice problem. If only one suit might provide a source for a passive lead, the failure to lead that suit might be because of force of it being dangerous or of a random decision to not make that passive lead. For instance, what if a person had the option of either a passive club lead or an aggressive diamond lead? If a passive diamond lead was possible, then the opponent might, in a sense, be capable of either attack. If, however, a passive diamond lead was not possible, then the person may have been boxed into an aggressive slub lead. The flexibility of the latter suggests, by restricted choice, that the passive diamond lead was not an option.

[jdonn]

cherdano, on Apr 4 2007, 12:00 PM, said:

jdonn, on Apr 4 2007, 10:36 AM, said:

That argument about the queen doesn't matter since it applies to both cards. After all if you play the ten it can be

<!-- ONESUIT begin --><table border=1> <tr> <td> <table> <tr> <th> </th> <th> <table> <tr> <td>  </td> </tr> </table> </th> <th> </th> </tr> <tr> <th> <table> <tr> <td> A9652 </td> </tr> </table> </th> <th> </th> <th> <table> <tr> <td> KJ74 </td> </tr> </table> </th> </tr> <tr> <th> </th> <th> <table> <tr> <td> QT83 </td> </tr> </table> </th> <th> </th> </tr> </table> </td> <td>  </td> </tr> </table><!-- ONESUIT end -->

I suppose you meant

---

(In your layout the T was the winning play anyway.)

Good point that is a much more accurate example. The point being that west might mistakenly duck no matter which card you play, since it's right on another layout.

[Halo]

In my world this LHO ducking just isn't happening when East has five - is East returning an ambiguous card? No.

[FrancesHinden]

My example didn't work - but there may be a layout where LHO might duck when you play the Q and not the 10. I've ducked by mistake myself in a slightly different position when the suit was running all along... it's not always easy to work these things out. The trick as declarer is to play confidently!

This isn't quite the right layout for it, because the pips don't work, but the standard successful swindle is a layout such as this one:

---

West leads the low pip to East's ace and declarer's 4, and East returns the 3 to South's Queen... if South started with QJ74 and East with A32 then West should duck this, but if South has Q42 then ducking looks very silly. (this isn't a 'swindle' as such because South's only legit chance is to play the queen)

Going off topic a bit here, but I think the principle is valid.

[HeartA]

bid_em_up, on Apr 3 2007, 10:26 AM, said:

Why are we in 3N instead of 6C, or at least 5C?

That's exactly the question I want to ask.

Now, I play 10.