  We examine the power of silent constant-space probabilistic verifiers that
watch asymmetric debates (where one side is unable to see some of the messages
of the other) between two deterministic provers, and try to determine who is
right. We prove that probabilistic verifiers outperform their deterministic
counterparts as asymmetric debate checkers. It is shown that the membership
problem for every language in NSPACE(s(n)) has a 2^{s(n)}-time debate where one
prover is completely blind to the other one, for polynomially bounded space
constructible s(n). When partial information is allowed to be seen by the
handicapped prover, the class of languages debatable in 2^{s(n)} time contains
TIME(2^{s(n)}), so a probabilistic finite automaton can solve any decision
problem in P with small error in polynomial time with the aid of such a debate.
We also compare our systems with those with a single prover, and with
competing-prover interactive proof systems.
