umberto straccia drriybhoisticnrit jul 13 2005 1248 gzrdaeecsberkeleyedu wrote consider following line reasoning let p proposition ronald born new york p infer q ronald born united states q infer r possible ronald born new jersey hand p infer possible ronald born new jersey arrived contradiction wrong note answer question familiarity modal logic needed inferring r q alone wrong forgot p still holds p pq q r umberto straccia wed 06 aug 2008 164427 0200 uai paradox