Some part of me wonders whether the David in question might not have
been <A HREF="http://www.best.com/~ddfr/">David D. Friedman</A>,
although I think Friedman and Smullyan are similar ages, so it's
unlikely that Friedman was a ten-year-old while Smullyan was an adult --
unless some space travel at relativistic velocities was involved
in the interim.