Explain consciousness. Or not. If you like your mysteries solvable, explicating mind can be a problem. The hard problem, though, might be to resist trying, to let sleeping dogs iie, so to speak, or, more precisely, to let them dream. Tom Stoppard is interested in hard problems, in describing them if not exactly trying to solve them. And so we have here an exploration of some of the more regular metaphysical dichotomies--mind v. matter, neuropsychology v. behavioral psychology, material v. psychic reality--with no resolution in sight. Stoppard gets the arguments right, but he doesn't root these quandaries as successfully in character--and in feeling--as he has before. THE HARD PROBLEM is an interesting play, but it's not an especially involving one; it privileges curiosity over sympathy. When we can't really know how we exist, we're basically left to choose between, as Stoppard has it, miracles or coincidences. What's missing here is a more ample depiction of the emotional challenges that can come from negotiating, as we must, these constant tensions.