The state of the game and of the score will often direct as to a finesse late in a hand. Thus, if you hold a winning card, and want one trick to save or win the game, of course you should not run any risk. A finesse against even one card is generally wrong, if, by playing otherwise, you prevent the adversary from scoring three or five. A finesse is almost always bad, if by not finessing you insure the odd trick, as that makes a difference of two to the score. In the opposite case, a finesse is generally right (sometimes even against more than one card), if its success gives you the odd trick, or puts you at the score of three or five.
The considerations as to finessing and the course of play generally, that come in as the hand proceeds, are so complicated, and depend so much on inferences from previous play, and on the state of the score, that one can scarcely do more than to state a few broad rules, and to add some examples. Illustrations of the conduct of the hand at advanced periods will be found in Sections 17 and 18 (pp. 134-155), and more in the hands.
The fourth player having, with a few exceptions, merely to win the trick, if against him, his play involves no further development of general principles.
The exceptional cases, where the fourth hand should not win the trick though he can, or should win his partner's trick in order to get the lead, depend so much on the previous fall of the cards, that they can best be illustrated in the hands.
In the foregoing chapters it has been incidentally stated that you should
9. KEEP THE COMMAND OF YOUR ADVERSARY'S SUIT: AND
10. GET RID OF THE COMMAND OF YOUR PARTNER'S SUIT.
The reasons will be obvious to those who are familiar with the previous pages; in the first case, you obstruct the adversaries' suits, and prevent their establishing them; in the second case, you assist in clearing the suit for your partner.
Thus, with ace and queen only of a suit led by your partner, if you win with the queen, play out the ace at once; but, if the suit is led by your adversary, keep the ace in your hand. If you play out the winning card of the opponent's suit in hopes of trumping the next round, which is often done by those who play a trumping game, you do just what the adversaries want; for the lead of the ace gives them valuable assistance towards bringing in their suit when trumps are out.