鏡乃日常用物，故古人每以之為喻以說理。始則以鏡喻史，繼則以鏡喻心，乃從歷史之鑑戒轉向心性哲理之推明。儒道釋三家皆有其鏡喻，然由於對心有不同之觀照，故取鏡為喻以言心者，自有不同之思理。就儒道兩家言，莊子首先以鏡比喻至人之用心，取鏡映像而不藏像之義，喻至人之心任物去來，應物無累；而鏡之不擇物而映像，亦以喻至人能忘物我，包容眾人。荀子取水為鏡以喻心；水平靜則澄清而能明照形貌，喻心虛靜則清明而能明察是非。《淮南子》之鏡喻顯然承於莊子，以鏡子明亮則無塵垢之染，喻心神清虛則無嗜欲之亂，如是則能對政事有分明之照察。理學家程明道以鏡子能當下照物分明而不留影，喻聖人無心應物，是以能通達物情而不留情，此顯然採自莊子之喻。朱子以明鏡止水喻心，當有取於荀子，然注重涵養心氣、窮究物理以全幅彰顯心知之明。陽明以明鏡隨物現形而不留影，喻良知感應萬物而無所著，殆兼承莊子及佛家鏡喻之說，而更重私欲之克制。佛家以鏡為喻言理處較儒道二家為多，大抵以鏡像之非真喻萬法之虛幻，以鏡能明照萬像喻性能顯現萬法，鏡隨物之異而現其像，喻佛菩薩隨順眾生所樂見而示現法身。然性與萬法之關係則隨說法系統之異而不同，如華嚴系與法華系即有性起與性具之別。

As something common in daily life which had been frequently used as metaphor by ancient Chinese to explain historical experiences in the first place, followed by pointing out philosophical truths implied in human mind and nature, mirror metaphor, as being compared to the concept of mind occurring in Confucian, Daoist, as well as Buddhist texts, has been taken to refer to different types of philosophy. Zhuangzi, for instance, is well known for connecting mirror to the mind of the highest man (zhi ren), where a similarity between the former’s reflective function and the latter’s emptiness is logically constituted. As different from Huainanzi which claims that political affairs should be based on the emptiness of mind, as being analogical to keep a mirror without polluted, like what Zhuangzi claims, Xunzi focuses on the connection between water and mind, arguing that one is unable to make judgments unless one keeps his or her mind peace, just like there would be no image on the water unless it stops flowing. By emphasizing mirror’s imaging things without gripping, Cheng Mingdao, obviously influenced by Zhuangzi in terms of the metaphor, praises the sages for their respect for the essence of the myriad things by responding to them naturally. Zhu Xi, other Confucian who learns from Xunzi, refers to the mind just as a mirror, where he provides a teaching that both mind cultivation and physical understanding are contributive to mind-enlightenment. Besides, paying more attention to desire restraint than scholars as mentioned, Wang Yangming, who combines Zhuangzi’s mirror metaphor with Buddhist, takes his concept of liang zhi as something responding to things without attachments, as parallel to mirror’s appearance according to what things are present. It should also be mentioned that comparing with Confucianism and Daoism, Buddhism has the greatest frequency of using mirror metaphor, where the world humans are living is said to be so illusory, just like no reality should be shared by images reflected on the mirror. But, given the truth that the essence of mirror should be defined by its function of lighting up its (various) objects, it is also analogically claimed with a great number in the Buddhist texts that all the dharma are revealed by the function of prakrti, and that the Bodhisattva would realize itself, in accordance with the aspiration of all living creatures, as infinite dharmakaya, respectively. Definitely, how prakrti relates to the dharmakaya should depends on what teaching system one claims, and this is why there is an idea held by Hua-Yen system that prakrti serves as an origin of dharmakaya, as contrary to Fa-Hua system, which claims that all dharmakaya are essentially implied by prakrti.