Source: INFERENCES AT BRIDGE CHAPTER I GENERAL INFERENCES by W. Dalton
It is a well-known fact that a large number of people go through life with their eyes tight shut, or at any rate heavily bandaged. They see and realise the ordinary events which occur within the circle of their own immediate surroundings, under their noses, so to speak, but beyond that they do not pretend to look at all. They never attempt to read between the lines, to put two and two together, and to draw inferences, correct or otherwise, from what they see and hear.
Precisely the same principle applies to the bridge table. There are many bridge players—we all know them by the score —who are quite au courant with the general principles and conventions of the game, who play their cards intelligently and well, and who consider themselves, and are considered, good sound players, but who never dream of rising to a height beyond that, or of drawing even the most simple inferences from what they see happen during the play of a hand. To tell such a one that, in a No Trump game, when he holds king and two others of a suit of which the dummy has queen, knave, ten to five or six, and the dealer does not touch that suit, the ace of it is marked to an absolute certainty in his partner’s hand, is to talk to him in a language which he does not understand, yet this is the most simple of all inferences.
There are many others of the same kind. They present themselves in almost every hand which is played, but a large majority of people, who play what they are pleased to call intelligent bridge, allow them to pass by utterly unheeded. Such players simply do not notice the obvious inference, or, if some idea of it does flash across their mind, they fail to make a mental note of it at the time for use later in the hand. Herein lies the one and great secret of the success of the first-class player, and thus he sometimes scores so heavily. It is not by playing any extraordinarily fine coups, or by wriggling cleverly out of difficult positions, that he gains his advantage.
It is by drawing inferences at the time, recording them on the tablets of his memory, and acting on the information thus acquired, that he appears at times to possess an almost intuitive knowledge of how the cards are placed. There is really no intuition about it at all it is simply close reasoning coupled with a careful observation of the fall of the cards. One day I was sitting behind a friend of mine, watching him play a hand. He is a very keen bridge player, who fancies himself and his own methods more than a little. The score was one game all. His right-hand adversary dealt and passed, finally he ended as heart contract declarer. His hand and the dummy’s were :
The first 5 tricks were played as follows: 
A, K and 
J, declarer played the Q, North the K and the declarer won the trick with the A, to continue with the trump ace and a nother trump, my friend won with his 
K.
My friend then had to lead. After considerable thought he led the 6, the dealer made the 9, draw the last trump to continue with the 10 and 8, throwing clubs from dummy winning 10 tricks. I held my peace; but, after it was over and all the cards known, my partner’s friend said to him : » I wonder you did not put me in with a club so that I could give you another diamond to make your last trump.» My friend answer, in a tone of withering sarcasm, was : » I would have done so if I had possessed the faculty of seeing through the backs of the cards, but unfortunately I do not possess it. If I had led a club and the dealer had had the ace we should never have made a trick in the suit at all, and I had no possible means of knowing where the ace was. The spade lead was much the best chance of putting you in.»
Now, how could the dealer have had that ace of clubs ? He had already produced two aces, the ace of spades and the ace of trumps, and was it possible —was it conceivable—that he would have passed the declaration, at that point of the score, with three aces in his hand ? Here was an inference which was absolutely sticking out, and which one would have expected to be apparent to the merest tiro at the game, but it was missed, and missed by a player who invariably watches the fall of the cards, and who can generally tell you every card that has been played. He knew perfectly well that the dealer had played those other two aces, but the faculty of putting two and two together and of deducing from what he had observed was altogether wanting.
The most certain of all inferences at bridge is that, when the dealer, after passing the declaration, produces two aces from his own hand, he cannot have a third, and that, therefore, the missing ace or aces are marked to an absolute certainty in one’s partner’s hand. A glance at your own hand and at the cards exposed in the dummy will generally suffice to clear up this point. In these advanced days no player would dream of passing the declaration with three aces, however weak the rest of his hand might be, therefore you have this one certainty to begin basing your inferences upon, that when the dealer has passed the declaration to his partner, he cannot possibly hold three aces. Bear this in mind, and make a mental note of it, and remember it the next time your opponent passes. It probably will not be of any assistance to you in that particular case, but at any rate you will have begun to practise the faculty of drawing inferences, and sooner or later that simple inference, that very obvious little inference, will be found to be of great service to you, and to materially assist you in saving a game.