"You have one great advantage," he told her. "You know nothing whatsoever of chess--so you will be able to write about it understandably for your readers." He swallowed half his demitasse and smacked his lips. "As for the Machine--you _do_ know, I suppose, that it is not a humanoid metal robot, walking about clanking and squeaking like a late medieval knight in armor?" "Yes, Doc, but...." Sandra found difficulty in phrasing the question. "Wait." He lifted a finger. "I think I know what you're going to ask. You want to know why, if the Machine works at all, it doesn't work perfectly, so that it always wins and there is no contest. Right?" Sandra grinned and nodded. Doc's ability to interpret her mind was as comforting as the bubbly, mildly astringent mixture she was sipping. He removed his pince-nez, massaged the bridge of his nose and replaced them. "If you had," he said, "a billion computers all as fast as the Machine, it would take them all the time there ever will be in the universe just to play through all the possible games of chess, not to mention the time needed to classify those games into branching families of wins for White, wins for Black and draws, and the additional time required to trace out chains of key-moves leading always to wins. So the Machine can't play chess like God. What the Machine can do is examine all the likely lines of play for about eight moves ahead--that is, four moves each for White and Black--and then decide which is the best move on the basis of capturing enemy pieces, working toward checkmate, establishing a powerful central position and so on." * * * * * "That sounds like the way a man would play a game," Sandra observed. "Look ahead a little way and try to make a plan. You know, like getting out trumps in bridge or setting up a finesse." "Exactly!" Doc beamed at her approvingly. "The Machine _is_ like a man. A rather peculiar and not exactly pleasant man. A man who always abides by sound principles, who is utterly incapable of flights of genius, but who never makes a mistake. You see, you are finding human interest already, even in the Machine." Sandra nodded. "Does a human chess player--a grandmaster, I mean--ever look eight moves ahead in a game?" "Most assuredly he does! In crucial situations, say where there's a chance of winning at once by trapping the enemy king, he examines many more moves ahead than that--thirty or forty even. The Machine is probably programmed to recognize such situations and do something of the same sort, though we can't be sure from the information World Business Machines has released. But in most chess positions the possibilities are so very nearly unlimited that even a grandmaster can only look a very few moves ahead and must rely on his judgment and experience and artistry. The equivalent of those in the Machine is the directions fed into it before it plays a game." "You mean the programming?"