以过去、历史为镜鉴，可以了解现在并预知未来。也说“鉴往知来”“知古鉴今”。“鉴”本指镜子，引申为借鉴、参照、审察、考察。所谓“鉴古”“鉴往”“知古”主要指总结历史上朝代、国家兴衰成败的经验教训，考察历史人物的言行事迹以及是非善恶，来为现实的国家治理和个人的道德修养服务。“知今”“鉴今”“知来”则是了解现在，以现在为鉴，预知未来。古代执政者为了使自己的决策符合国情、民情，具一定合理性，非常注重从历史中吸取经验教训，避免重蹈覆辙。它包含着对于历史的现实意义和现实的历史景深的双重关注。与“前事不忘，后事之师”意思接近。
Reviewing the past helps us understand the present and predict the future. It is also said that "reviewing the past we understand the future" and "knowing the past we understand the present." The Chinese word jian (鉴) can mean "mirror" and hence to "review the past" as if in a mirror, "understand the past," or "gain knowledge of the past." The lessons of the rise and fall of dynasties and states, the words and deeds of historical figures, as well as right and wrong, and good and evil, help govern the country and improve personal morality. "Understanding the present," "reviewing the present," or "understanding the future" means predicting the future based on the present. The rulers of antiquity saw it as extremely important to draw lessons from history in order to avoid past mistakes and justify their policies by making them conform to the needs of the country and people. The concept of "reviewing the past to understand the present" stresses both the practical significance of history and the historical depth of things present. It is similar to the concept that "past experience, if not forgotten, is a guide for the future."
引例 Citations：
◎监前世之兴衰，考当今之得失，嘉善矜恶，取是舍非。（司马光《资治通鉴》）
察看前代政权的兴衰，考察当今的得失，赞美善德，戒惧恶行，采纳正确做法，放弃错误做法。
It is advisable to review the rise and fall of previous dynasties and the achievements and failures of the present dynasty, to commend the good, condemn the evil, and adopt what is right and discard what is wrong. (Sima Guang: Memorial on History as a Mirror)
◎知往鉴今，驱曹荡吴，非同小可也。（无名氏《太平宴》第一折）
了解过去，作为现在的镜鉴，驱除和消灭曹魏、孙吴，这是了不起的事业。
It is of great importance to review knowledge of the past to help understand the present, expel the invasion of the State of Wei and wipe out the State of Wu. (A Peace Banquet)
推荐：教育部 国家语委
供稿：北京外国语大学 外语教学与研究出版社
责任编辑：钱耐安
