In the age of the imperial exams, a man with no degree was often looked down on as a mere commoner.
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culture
Best known from 刘禹锡's 《陋室铭》: 谈笑有鸿儒，往来无白丁 (I talk and laugh with great scholars; no unlettered men come and go). 白丁 is the opposite of 鸿儒, a great scholar: 白 is 'plain, without rank' and 丁 'an adult man'.
