Nobody knows what Kevin Garnett will say or do when Carmelo Anthony steps onto the floor in Boston on Thursday night, when the Knicks and the Celtics meet for the first time since Garnett’s on-court posturing turned Anthony into a backstage vigilante early this month in New York.

That is the point. Garnett is as unpredictable as he is emotional. He is as calculating as he is quick-witted. If that sounds contradictory, Garnett has always come across as a little stranger than the average professional basketball player, and at least that much sharper.

When he announced at a Chicago pizza restaurant in May 1995 his intention to join the N.B.A. right out of high school, he was asked if he had consulted with Moses Malone or Shawn Kemp, who had successfully made the leap without playing in college.

No, Garnett said, he had called Bill Willoughby, who had not lasted long as a pro, to determine what pitfalls to avoid.