Lu Jiuyuan 陸九淵 (1139-1193), courtesy name Zijing 子靜, style Cunzhai 存齋 or Xiangshan Jushi 象山居士 (Lu Xiangshan 陸象山), was a Neo-Confucian philosopher of the early Southern Song period 南宋 (1127-1279). He is the most important early representative of the "School of the Mind" (xinxue 心學).
He hailed from Fuzhou 撫州 (modern Jinxi 金溪, Jiangxi) and earned his jinshi degree in 1172. As a state official he occupied posts like assistant magistrate (zhubu 主簿) of the district of Jing'an 靖安, instructor at the Directorate of Education (guozi zheng 國子正), master of the shrine of the Chongdao Hall 崇道觀 in Taizhou 臺州, and military prefect (zhijun 知軍) of Jingmen 荆門.
His philosophy of the individual mind was developed in his youth, when he wrote that "the universe is in my own heart, and my heart is nothing else than the universe" (yuzhou bian shi wu xin, wu xin ji shi yuzhou 宇宙便是吾心，吾心即是宇宙). This idea became the core concept of his philosophy. It was a transformation of Cheng Hao's 程顥 (1032-1085) theorem that the individual mind or "heart" (xin 心) represented the universal or Heavenly principal (xin shi li 心是理). Lu Jiuyuan expanded this basic sentence and founded the theory of the individual heart as an expression of the universal principle or order. In this theory, he explained how an individual had to "enlighten the Heavenly principle" (ming li 明理), how to "raise his individual mind" (li xin 立心) to the same level as the universal mind, and how to "become a [good] person" (zuo ren 做人).
In 1175, Lu Jiuyuan participated in a conference of Neo-Confucians organised by Lü Zuqian 呂祖謙 (1137-1181), the famous Conference of the Swan Lake (Ehu zhi hui 鵝湖之會), and contradicted the great philosopher Zhu Xi 朱熹 (1130-1200) in several dogmatic questions. While Zhu Xi became the leader of the School of the Universal Principle (lixue 理學), Lu Jiuyuan headed the School of the Mind.
Lu Jiuyuan's propositions are the following: The foundation of the universe was, just as in the teachings of the brothers Cheng Hao and Cheng Yi 程頤 (1033-1107), and Zhu Xi, the "universal principle" (li 理). While the brothers Cheng and Zhu Xi saw the "universal principle" as an objective principle that governed all objects in the universe as an exterior force, Lu Jiuyuan was of the opinion that the universal principle was a subjective principle that was implanted in the mind (xin, "heart") of each individual. The consequence was that each individual mind (yi xin 一心) was endowed with one individual principle (yi li 一理). In spite of this individual character, the "personal mind" was in the end identical to the universal principle (xin ji li ye 心即理也 "the mind IS the principle") that was implanted into the mind of each individual, so that they were in fact one (wu er 無二 "there are no to different [orders]"). Each human possessed this kind of individual mind, which was at the same time identical to the universal principle and a kind of "fundamental mind" (ben xin 本心).
The universal principle was not produced out of the mind of each individual, but was generated by birth as a kind of universal inheritance from Heaven (tian zhi suo yi yu wo zhe 天之所以予我者 "something that Heaven has provided to me"). This common origin made sure that the mind of each individual shared common features and was not wholly separated and independent from the mind of others, but was in fact all the same as the mind of contemporaries, of the sacred rulers of the past, or the descendants of coming generations. Lu Jiuyuan's theory is another explanation for Meng Ke's 孟軻 (385-304 or 372-289 BCE, Mengzi 孟子) observation that all humans would hurry to rescue a child that has fallen into a well. The mind, originating in the universal principle, was so vast that persons able to wholly explore this "universal mind" would be able to wholly comprehend Heaven. In the eyes of a Confucian scholar, the will of Heaven, transformed in the universal order, was this kind of society that Confucius had explained, namely one in which social relations (lunli 倫理) were observed and all individuals behaved in a moral way (daode 道德). For Lu Jiuyuan, the individual mind was identical to the principle of the universe, and thus automatically steered each human to behave in the right way.
Although the individual mind was inherited by nature, it was not easy for all humans to recognize what the universal principle embedded in this mind actually was. It was therefore necessary to discover the original structure of the universal principle (faming benxin 發明本心) in one's heart. Self-contemplation and cultivating social relationships were required to find out what the original "universal mind" was. It could not be found in others or outside the self, but it could be detected inside the own heart, and then be controlled, nourished (yang xin 養心) and preserved (cun xin 存心) in an easy and simple way (yi jian gong fu 易簡功夫). Only this method would ensure that the original mind of the universe could be fostered (ji shan 積善 "accumulate the good", ji yi集義 "assemble proper conduct", zhi de 知德 "know the virtue", jin de 進德 "promote virtue") in one's own heart without outer forces being able to distract the individual from this universal mind. Humans had to strive for self-improvement (zi wo wan shan 自我完善), self-awareness (zi wo renshi 自我認識), and for the reduction to the basics by way of introspection (zi wo fan sheng 自我反省). The way to the universal mind could be hampered by the quest for (unnecessary) things (wu yu 物欲). Lu Jiuyuan saw this as a kind of skin disease that had to be "peeled off" (boluo 剝落). This kind of liberation from improper quest for vain things could only be achieved with the help of friends and instructors.
The Confucian Classics were, in Lu Jiuyuan's eyes, important writings that supported the quest or the "good mind" (liangxin 良心). They were not to be treated as orthodox texts but as a means of inspiration that were written in attention to the individual, and by which "I can fix my mind on" (liujing zhu wo 六經注我, wo zhu liujing 我注六經). Contrary to Zhu Xi, Lu Jiuyuan did not advocate the thorough study of all things and all books, but suggested to focus on the core corpus of the Six Classics, and, of course, on the universal mind inside oneself, instead of searching it the ancient writings. Realities could be perceived out of one's own heart, and not only from a more "objective" distance. Lu Jiuyuan said, "the ten thousand things are readily to be found in myself" (wanwu jie bei yu wo 萬物皆備于我).
Lu Jiuyuan did not compile books, but instructed his disciples orally. Only after his death his son Li Chizhi 陸持之 (1156#1210) and some disciples began to write down his propositions and theories and assembled them, together with his non-scholarly writings, in the book Lu Xiangshan wenji 陸象山文集 (also called Xiangshan xiansheng wenji 象山先生全集). This book is in modern editions called Lu Jiuyuan ji 陸九淵集.
Contemporarians and later adherents of Zhu Xi's school criticised Lu Jiuyuan for his apparent individualism that opposed the objective character of the universal order. Lu's writings were therefore overshadowed by the more orthodox teachings of Zhu Xi and his school.