A labyrinth is more than a metaphor for our quest for knowledge; it is. . .methodologically equivalent to our logic."" Thus does physicist/philosopher Poundstone here elaborate his thesis on the nature of belief, the search for truth, the problem of knowledge. His is at once a book that deals at an elementary, accessible level with the nature of deduction, induction, simple propositional logic and puzzles, and a profound treatment of epistemological questions--of how we know what we know; what constitutes proof and evidence, belief and fact. The catch (and what becomes an oft-repeated theme and variation here) is that there are limits to knowledge; it is ""frail"" in that we can cite instances in which reason cannot prevail, even with supercomputers committed to supertasks over supertime. There is a whole class of ""NP-Complete"" problems (like the find-the-shortest-round-trip-route-among-n-cities) that entail astronomical permutations as ""n"" increases. For all we know, most knowledge is like that; in fact, ""For all we know"" is in itself one of Poundstone's favorite themes as he discourses on philosophical conundrums. For all we know, we are disembodied brains in vats. . .for all we know, the universe was created five minutes ago. . .for all we know, each of us has a twin able to predict our behavior because the twin is fired in a rocket traveling at near the speed of light. These images and examples abound as Poundstone examines paradoxes old and new, from the lying Cretans to the prisoner's dilemma. As interludes there are pleasing riddles, entertaining explanations, and always, a winning style. And there is more than enough here in the way of analysis of mazes, Turing machines, maps, ciphers and orders of infinity to intrigue, stimulate, and reward--even, and maybe because, you may have to read the same paragraph over again to get the point.