Today's game illustrated Mr. Kasparov's capacity for learning from brief experience, as he consistently sought positions where he had discerned, from the previous games, that the computer has trouble -- where the short-term position is cloudy and it has no imminent tactical objective.

"It is weakest in a position where it doesn't have a plan," Mr. Kasparov said. "You have to limit its unlimited potential, you have to be careful not create weaknesses in your own position, not to leave hanging pieces, not to leave a king threat. You have to play solid, positional chess because any mistake will be punished by the machine more severely than by a human player."

Mr. Kasparov, who lost the opening game of the match last Saturday, to the cheers of the I.B.M. research team that developed Deep Blue and to the gasps of almost everyone else, rebounded on Sunday with a victory. There followed two draws. Then, in game 5, Mr. Kasparov offered Deep Blue a draw, but the computer (actually its programmers; Deep Blue can be, but isn't, programmed to offer or accept a draw) declined.

Mr. Kasparov roared to a decisive win.

"We were surprised by the offer of the draw, because it came so early in the game," said C.J. Tan, I.B.M.'s project manager for the development of Deep Blue, who said he discussed the offer -- after Mr. Kasparov's 23d move -- with Murray Campbell, an I.B.M colleague, and Joel Benjamin, a grandmaster who is advising the Deep Blue team, and though by the analysis of Deep Blue itself the computer was in a slightly disadvantageous position, they decided to press on. It was a decision that surprised many chess experts, who saw no winning chances for Deep Blue's white pieces.

There are essentially two thought algorithms, or methods, of chess playing. In one, the brute force mode that is the strength of the computer, all possible moves and their consequences are analyzed as far into the future as possible. In the other, which approximates how a human being plays chess, a selectivity function (in a human, this is instinct and experience) limits the search and analysis to only the most promising moves and their consequences.

Deep Blue, which was developed at I.B.M.'s Thomas J. Watson research center in Yorktown Heights, N.Y., over the past six years, is equipped with powerful parallel processing technology that allows it to search more than 100 million chess positions a second. But it also has the most highly sophisticated chess evaluation software yet developed and an extensive data base of chess games from which to draw for decision-making. The combination of factors has engendered a formidable amalgam of calculating speed and chess knowledge. Mr. Kasparov, who once doubted that any machine would be able to beat him, acknowledged that the computer's pure calculating power (which is routinely referred to as brute force) had finally brought technology up to speed in chess thinking.

"For the first time I saw something approaching artificial intellect," he said. But some players and scientists question whether that's true -- like David Gelernter, the Yale art historian and computer scientist, believes that the achievement belongs only to the builders of the computer

"This match is almost a demonstration that intelligence is not the only way to win at chess," Mr. Gelernter said. "Brute force, sheer computational mass, is something that can substitute for intelligence."