Eric Temple Bell, a mathematician and science fiction author, was born in Scotland but moved to the United States when he was 15 months old. He said, “Euclid taught me that without assumptions there is no proof. Therefore, in any argument, examine the assumptions.”

You make many assumptions at the bridge table, based on the bidding and cards played. If those assumptions are correct, you will make a lot of winning decisions.

In today’s deal, East drew a conclusion that had no validity and gave away a game. South was in three notrump. West led the spade queen in answer to his partner’s overcall. What should have happened?

The auction was straightforward. East was right to overcall one spade for two reasons: His side might have been able to outbid the opponents, and to help partner with his opening lead. Then South jumped to three no-trump with sufficient points for game and two spade stoppers.

At the table, East encouraged with the spade 10 under his partner’s queen. However, he is still waiting for his partner to lead another spade. East’s assumption that his partner had started with two spades was not valid.

South allowed the spade queen to hold the first trick, took West’s diamond shift, and played on clubs to establish 10 tricks. He lost only one spade and two clubs.

As you have noticed, East should have overtaken the spade queen with his king. This costs a trick only when West has the spade queen and jack, which is most unlikely given South’s jump to three no-trump.