The Lunqi 論氣 "A Discussion of Substance" is a book on physics written by the late Ming period 明 (1368-1644) scholar Song Yingxing 宋應星, who is better known as the author of the technical book Tiangong kaiwu 天工開物. The Lunqi is composed of four parts called Yeyi 野議, Tantian 談天, Silian shi XXX 思憐詩. It was printed during the Chongzhen reign 崇禎 (1629-1644) and was only rediscovered in the Jiangxi Library 江西省圖書館 and republished in 1976 by the Renmin Press 人民出版社出 in Shanghai in an edition annotated by Qiu Feng 丘鋒. The text discusses the nature of matter (qi 氣), its transformation, its sounds, and negates the ancient belief that the agent water vanquishes fire, and instead proposes the theory of water and dust, water and wind, and coldness and heat. In the eyes of Song Yingxing the ancient belief in the Five Agents or elements (wuxing 五行) is antiquated and had to be replaced by a more suitable concept of one type of matter that has different shapes and aggregate statuses, and that the ten thousand beings are made of this one substance. In his eyes, things that have no shape, is air (qi 氣), and what is not air, is solid matter. Between these two aggregate states are fire and water. Air becomes solid matter by transformation, and the latter can again disaggregate into air. Voice, sound and wind are also products of the basic substance by an interchange and echo between air and air. Heat and coldness are a result of various shares of these factors in the substance, like seventy to thirty.|
Source: Gao Liushui 高流水 (1996). "Lunqi 論氣", in: Feng Kezheng 馮克正, Fu Qingsheng 傅慶升 (ed.), Zhuzi baijia da cidian 諸子百家大辭典, Chengdu: Sichuan renmin chubanshe, p. 433.