  We consider players that have very limited knowledge about their own
valuations. Specifically, the only information that a Knightian player $i$ has
about the profile of true valuations, $\theta^*$, consists of a set of
distributions, from one of which $\theta_i^*$ has been drawn.
  We prove a ``robustness'' theorem for Knightian players in single-parameter
domains: every mechanism that is weakly dominant-strategy truthful for
classical players continues to be well-behaved for Knightian players that
choose undominated strategies.
