◎ 数往知来 shǔwǎng-zhīlái[deduce what likely to happen in the future by reviewing what has taken place in the past;know the future by thinking of the past] 追溯过去,可以预测未来 -----------------国语辞典:语本《易经.说卦》:「八卦相错,数往者顺,知来者逆。」指根据已过去的事来推测,就可预知未来。明.陆容《菽园杂记.卷一》:「洪武中,朝廷访求通晓历数,数往知来,试无不验者,必封侯,食禄千五百石。」近温故知新
◎ 数典忘祖 shǔdiǎn-wàngzǔ[give all the historical facts except those about one's own ancestors;forget one's ancestors and ancestral tradition] 据《左传》记载,春秋时晋国大夫籍谈没有回答好周天子的提问而被周天子讽刺为“数典而忘其祖”。后比喻忘掉自己本来的情况或事物的本源 -----------------国语辞典:典,指过去的礼制、历史。数典忘祖谓叙述过去礼制历史时,却忘掉祖先原有的职掌。语本《左传.昭公十五年》:「籍父其无后乎?数典而忘其祖。」比喻忘本。《儿女英雄传.第二八回》:「只是如今弄到用起锦绣绸缎手巾来,连那些东西,也都用金银珠宝作成者,便是数典而忘其祖,大失命题本意了。」亦可比喻对本国历史或自己祖先历史的无知。如:「如今崇洋媚外,数典忘祖的人可多著呢!」反饮水思源