主语：He
谓语：believe
宾语从句：that this very difficulty may have had the compensating advantage of forcing him to think long and ...and in his own observations
难点：是宾语从句中的宾语由动名词短语the compensating advantage 和 forcing him复合组成,其中动词不定式短语to think long and intently 作为动名词短语forcing him 的宾语补足语.介词短语about every sentence 作为动词不定式to think 的状语.and thus 后面的成分是从句的结果状语