An interview with Kubrick appeared in the September '68 issue of PLAYBOY magazine.

"You're free to speculate as you wish about the philosophy and allegorical meaning of the film – and such speculation is indication that it has succeeded in gripping the audience at a deep level – but I don't want to spell out a verbal road map for 2001 that every viewer will feel obligated to pursue or else fear he's missed the point."

It's a very interesting interview. And, yes, I read it for the articles.