Cheng Hao 程顥 (1032-1085), courtesy name Bochun 伯淳, style Mingdao Xiansheng 明道先生, and his brother Cheng Yi 程頤 (1033-1107), courtesy name Zhengshu 正叔, style Yichuan Xiansheng 伊川先生, were two important philosophers of the Northern Song period. They can be called the veritable founders of Neo-Confucianism. They are called the "two Chengs" (Er Cheng 二程), Cheng Hao being the "Older Cheng" (Da Cheng 大程), and Cheng Yi the "Younger Cheng" (Xiao Cheng 小程). Both are counted among the five important thinkers of the Northern Song (Beisong wu zi 北宋五子), the others being Shao Yong 邵雍 (1011-1077), Zhou Dunyi 周敦頤 (1017-1073), and Zhang Zai 張載 (1020-1077). Because they hailed from Luoyang 洛陽 (today in Henan), their school is called the Luoyang School (Luoxue 洛學). Much of the individual teachings of the two brothers cannot clearly be attributed to one person, and are therefore brought together in books about the “teachings of the two Chengs”, like Er Cheng cuiyan 二程粹語, Er Cheng yishu 二程遺書 and Er Cheng waishu 二程外書. The complete collection Er Cheng quanshu 二程全書 includes, among others, the collected writings Mingdao Xiansheng wenji 明道先生文集 and Yichuan Xiansheng wenji 伊川先生文集 (Er Cheng wenji 二程文集).
Cheng Hao obtained his jinshi degree with the age of 25 sui and was given a post in the local administration where he was very successful. During the reign of Emperor Shenzong 宋神宗 (r. 1067-1085), Cheng was recommended as companion for the heir apparent (taizi zhongyun 太子中允) and then made investigating censor (jiancha yushi 監察御史). At the time Counsellor-in-chief Wang Anshi 王安石 (1021-1086) carried out his comprehensive reforms (xinfa 新法 "the new laws"), on which Cheng Hao made critical remarks, arguing that the reforms aimed at increasing government revenue (xing li 興利) and not at strengthening the virtuous rule of the emperor (shang de 尚德). He was therefore transferred to functions outside Luoyang, first as notary of the administrative assistant (qianshu panguan 簽書判官) of the military prefecture of Zhenning 鎮寧軍, and then as district magistrate of Fugou 扶溝. During that time, he often returned to Luoyang, where he and his brother held lectures on philosophy. When Sima Guang 司馬光 (1019-1086) was made chief counsellor, Cheng Hao was called back into the central government as assistant minister of the Court of the Imperial Clan (zongzheng cheng 宗正丞). Yet he did not take over this post and passed away shortly later.
In 1220, Cheng Hao was bestowed the posthumous title of Chungong 純公 "Duke of Purity", and was in 1241 invested as Earl of Henan 河南伯. From then on, the altars of Confucius temples included a spiritual tablet for him.
Cheng Yi, then aged 18 sui, once submitted a memorial to the throne in which he urged Emperor Renzong 宋仁宗 (r. 1022-1063) to keep to the rule of the "royal way" (wangdao 王道) and care for the people's livelihood. He visited the National University (taixue 太學) in order to listen to the instruction of the philosopher Hu Yuan 胡瑗 (993-1059). At the age of 27 sui, he failed in the state examinations and decided not to try it again, nor to take up a post that was offered to him after recommendation. Instead, he remained a philosopher and teacher, instructing quite a few disciples. Only after the death of his brother Cheng Hao, and after recommendation by Sima Guang, he accepted the post of editor (jiaoshulang 校書郎) in the Imperial Library (mishusheng 秘書省) and lecturer (shuoshu 說書) in the Hall for the Veneration of Governance (Chongzheng Dian 崇政殿). Cheng Yi seemed to have been a polemical person and had a quarrel with the influential thinker Su Shi 蘇軾 (1037-1101). He was therefore transferred to a post in the local government, but soon returned and worked in the administration of the Directorate of Education (guozijian 國子監) in the Western Capital. Under the reign of Emperor Zhezong 宋哲宗 (r. 1085-1100), he was dismissed because of participation in the factional strife at court, but was then sent to Fuzhou 涪州 to serve in the prefecture. Cheng Yi was pardoned under Emperor Hui 宋徽宗 (r. 1100-1125), but soon again came under the supervision of the authorities. The political atmosphere was so tense at the time that his disciples did not even dare to participate in his funeral. In 1220, Cheng Yi was bestowed the honorific title Zhenggong 正公 "Duke of Rightness", and was posthumously conferred the title of Earl of Yiyang 伊陽伯.
Cheng Hao was a disciple of Zhou Dunyi, who instructed the young man to pursue the study of the "Way" (dao 道) in the teachings of Confucius (Kongzi 孔子, 551-479 BCE) and Yan Hui 顏回 (Yanzi 顏子, 521-481 BCE), but Cheng Hao read not just Confucian texts, but also Daoist and Buddhist writings and the various "masters" (zhujia 諸家). In the end, he decided to focus on the Six Classics (liujing 六經), in which he finally was able to detect the Way. The Chengs also received ideas from the philosophers Shao Yong and Zhang Zai which found entrance into their teachings.
The Cheng brothers were inspired of the Daoist concept of the Way, a kind of principle inherent in all objects and beings, but called it "Heavenly principle" or "Heavenly order" (tianli 天理). This core idea was so important in Neo-Confucian teachings that this Western term is more or less used as identical to the Chinese word lixue 理學 "teachings of the principle". The "universal principle" determined the cosmic order, the natural order, as well as that of society. In this way, the Confucian idea of how society worked and human relationships, including social hierarchies, operated was led back to a kind of "law of nature". Moreover, the old concept of Heaven was replaced by the power of a "principle". A sovereign had to pursue the way of a sovereign (jundao 君道), and his ministers that of ministers (chendao 臣道). Deviations from this way ran contrary to the universal principle (guo ci ze wu li 過此則無理).
Yet Cheng Hao also altered Confucius_ conception of kindness or benevolence (ren 仁). Just like the universal principle, kindness was embedded in all objects and beings, and could be expressed in different form. Confucian virtues like righteousness (yi 義), rituals (li 禮), knowledge (zhi 知) and trust (xin 信) were just facets of kindness (jie ren ye 皆仁也). Kindness (ren) was the body (ti 體) of the natural principle, righteousness (yi) its application in concrete situations (yi 宜), rituals (li) served for differentiation (bie 別), wisdom or intelligence (zhi 智) to achieve knowledge (zhi 知), and trust (xin) to carry out things in practice (shi 實). While Confucius had defined kindness as a form of human relationship applicable to others – be they kinsmen or not – Cheng Hao saw kindness as a principle that was laid into the heart of every person, and thus part of the physical body. Moreover, this type of kindness did not just determine the relationship between humans, but made man brother and sister of all objects.
It was nonetheless only the superior man (shengren 聖人) who would be able to thoroughly pursue the Way of kindness. In old times, Confucius had appealed to "subdue one's self and return to propriety" (ke ji fu li 克己復禮). Cheng Hao instead proposed to "fix one's character" (ding xing 定性) to align it to the character of the natural principle embedded in one's heart. This was possible by making the heart quiet, just as the universe had been before the creation of objects. The superior man would thus forget about his emotions and outer disturbances (nei wai liang wang 內外兩忘) and surpass his self. The inner mind could be reconciled with outer circumstances by making sincere and keep in the heart respect towards oneself and towards others (cheng jing cun zhi 誠敬存之). Discarding private desires (qu ren yu 去人欲) would help to "preserve the Heavenly principle" (cun tianli 存天理) in one's heart.
With regard to the relation between knowledge and practice, Cheng Hao believed that if the mind travelled to Chang'an 長安, it was as if the body was going there. Perfect knowledge would be able to replace action. Because everything was embedded in one's heart, it was not necessary that a learning person had to search in regions far away (xue zhe bu bi yuan qiu 學者不必遠求).
Even if the two brothers were unified in their novel interpretation of Confucianism, their teachings showed some differences. Cheng Hao laid more stress on the cultivation of one's inner heart, and probably influenced the Southern Song-period thinker Lu Jiuyuan 陸九淵 (1139-1193), the founder of the School of the Mind (Xinxue 心學). Cheng Yi lived much longer than his older brother, and most of the teachings of the two has therefore to be credited to the younger one. The great scholar Zhu Xi 朱熹 (1130-1200) refined his teachings and forged the "Neo-Confucian teachings of Cheng and Zhu" (Cheng Zhu lixue 程朱理學).
Cheng Yi explained that the universal principle was embedded in substance or matter, made out of condensed "air" (qi 氣). The physical character of objects and beings was determined by a continuous and permanent (sheng sheng 生生) interplay of Yin and Yang 陰陽. This thought went back to the Confucian Classic Yijing 易經. Accordingly, Cheng Yi defined the nature of all objects as complementary-dualistic (tian di zhi jian jie you dui 天地之間皆有對). Just like Yin decreased when Yang grew, goodness in human character would grow, while badness shrank.
After having taken shape, all objects were endowed with the universal principle (li) in its completeness. All things born were equipped with the potential for goodness (sheng zhi wei xing 生之謂性 "to be born means [to have a good] character"). With regard to humans, this meant that each man had the full potential to detect the universal Way in his mind. Objects, and persons alike, were a physical expression of the universal principle.
Cheng Yi coined the formula that the "human character is the universal principle" (xing ji li 性即理), and thus defined social relations, comportment and propriety as a kind of natural law. Following earlier concepts, Cheng Yi acknowledged that the original character bestowed by Heaven (tianming zhi xing 天命之性) differed from the individual character of man's physical substance (qizhi zhi xing 氣質之性, qi bing zhi xing 氣稟之性). While the former was identical to the universal principle (and thus fundamentally good, as daoxin 道心 "mind of the Way"), the concrete character of human individuals (renxin 人心 "the mind of men") was tainted by the environment and "the substance" (xing wu bu shan, er you bu shan zhe cai ye 性無不善，而有不善者才也). Pure matter led to good character, and slurry matter to bad character (qi qing he cai shan, qi zhuo ze cai e 氣清則才善，氣濁則才惡). The ancient philosopher Meng Ke 孟軻 (Mengzi 孟子, 385-304 or 372-289 BCE), holding that "humans were by nature good" (ren xing shan), spoke of the original principle, while later philosophers like Xun Kuang 荀況 (Xunzi 荀子, 313-238 BCE) or Yang Xiong 揚雄 (53 BCE-18 CE) had focused on the latter, and proposed methods to purify the human mind. It was Cheng Yi's success to bring these two views together, and make suggestions how man could go back to the original good principle.
The methods to find the original meaning of the Way were focusing of respect (zhu jing 主敬) towards oneself and towards others, and to achieve thorough knowledge (zhi zhi 致知). The detailed study of things would eventually lead to complete understanding and clarification of the universal principle and what was good (ming shan zaiyu ge wu qiong li 明善在乎格物窮理). Yet the "investigation of matters in order to perfect one's knowledge" (ge wu zhi zhi 格物致知), as described in the Classic Daxue 大學, did not refer to natural or technical studies, but the analysis of the true meaning of Confucian writings.
The thorough investigation of things would prove that each individual would have to follow his and her predetermined position in society, with concrete duties, like benevolence from the side of the father, and filialty form the side of the son, kindness performed by the sovereign, and respect by his ministers. These modes of conduct would lead to tranquillity (an 安) in society, corresponding to the quiescence that prevailed in the origin of the cosmos. The distinction between social hierarchies was a matter of the universal principle (li zhi dang 理之當), and the root of conduct (li zhi ben 禮之本).
A modern edition of the two brother's collected writings – philosophical and vernacular – is called Er Cheng ji 二程集 (Zhonghua Shuju, 1981).