The Mozi 墨子 "Master Mo" is a book compiled by the early Warring States period 战国 (5th cent.-221 BCE) philosopher Mo Di 墨翟 (ca. 476- ca. 390 BCE). He was probably born into a noble family in Song 宋 (with the name Muyi 目夷 or Motai 墨台) but lived the very common live of a wandering advisor and traveled from state to state. He served the rulers of Song, Lu 鲁 (where his family had lived for some time), Wei 卫, Qi 齐, Chu 楚 and Yue 越. There is one story that Mozi traveled day and night to reach the court of King Hui of Chu 楚惠王 (r. 488-432) to prevent him from beginning a conquest war against Song. He presented a memorial to the king of Chu but refused to be rewarded, and left. This story includes two of Mozi's main philosophical concepts, not to wage offensive war, and to refrain from luxury. In Qi he tried to stop Xianzi Niu's 项子牛 planned attack on Lu, but Mozi did not succeed. When the king of Yue offered him an office and a fief, Mozi brought forward the condition that the king would follow his advice. It is also known that he had a friendship with Lord Wen of Luyang 鲁阳文君, a nobleman of Chu.

Mozi's followers came from among the lower classes of society and were arranged in circles that were headed by a leader called juzi 巨子 "master of the saw" because all of them had to work for their subsistance. The Mohists were thus socially very different from the Confucians or Daoists whose representants came from among the lower nobility. There is no wonder that one of the most important postulations of the Mohists was austerity in government spending, and that their spirit was characterized by mutual help.
The book Mozi is said to have been 71 chapters long (bibliography Yiwenzhi 艺文志 in the official dynastic history Hanshu 汉书), of which later 18 went lost: The received Mozi has only 53 chapters. The bibliography Jingjizhi 经籍志 in the historySuishu 隋书 lists the book Mozi with 15 juan "scrolls", a number that is also recorded in all later bibliographies. The lost Song period 宋 (960-1279) catalogue Guange shumu 馆阁书目 entry was 61 chapters, in 15 juan, which might be a clerical error. The catalogue Zhongxing guange shumu 中兴馆阁书目 speaks of 13 chapters. The bibliography chapter in the encyclopediaTongzhi 通志, and the catalogues Zhizhai shulu jieti 直斋书录解题 and Guoshi jingji zhi 国史经籍志 divide the Mozi into only 3juan. Song Lian's 宋濂 Zhuzi bian 诸子辨 also speaks of 3 juan.

The core text of the Mozi covers twelve different philosophical themes, each treated in three different versions. The Qing period 清 (1644-1911) scholar Yu Yue 俞樾 explains this by the fact that after Mozi's death his school split into three traditions (Xiang Li 相里, Xiang Fu 相夫 and Deng Ling 邓陵) whose versions of Mozi's wordings (zi Mozi yue 子墨子曰 "Master Mozi says:") were not wholly identical. Later on the three versions were again unified in one book. Not all three versions are preserved for each chapter. Except the twelve philosophical treatises, there are a lot of diverse chapters dealing with advises for government and defense war. Very interesting are the chapters of the so-called Mohist Canon (Mojing 墨经, also calledMobian 墨辩 "Mohist disputes"), namely Jing 经, Jingshuo 经说, Daqu 大取 and Xiaoqu 小取. These chapters present a lot of definitions and thus can be seen as a first type of philosophical dictionary. They also include a lot of scientific terms, which shows that the Mohists (mojia 墨家) were a very practical school. Some chapters are of doubtful origin (Qinshi 亲士, Xiushen修身, and Suoran 所染) and might not be written by Mozi's disciples.

While the twelve core chapters are traditionally attributed to Mo Di himself, the Mohist Canon, in which China's oldest theory of logic is spread out, is surely of later date and includes cosmological concepts not yet ripe in Mo Di's time, like the Five Phases 五行 and the logical dictinction of "correct" and "not correct" (shi fei 是非). The Mohists discern logically between the three steps (sanbiao 三表) of concept (ming 名), argumentation (shuo 说), and conclusion (ci 辞), or debate (bian 辩), statement (lei 类), and arguments (gu 故). Each chapter of the Mohist Canon has a distinct focus. Jing shang and Jingshuo shang describe conceptual terms. Jing xia and Jingshuo xia deal with terms of definition and conclusion. The chapters Daquand Xiaoqu speak of reasoning, argumentation and of terms in respect of comparison. Inspite of this theoretical background the chapters of the Mohist canon deal with very concrete and practical matters, like the physical and philosophical explanation of comprehension and the connection between perception and reasoning. In the field of physics the Mohists were interested in mechanics, optics and geometry. Through the ages the six chapters of the Mohist canon have suffered and are full of writing errors.

Epistemology was an important part of Mohist thought. Cognition was able through the eyes and ears. What is perceived by these sensual organs is, in Mozi’s eyes, reality (wen zhi jian zhi, ze bi yiwei you 闻之见之，则必以为有 "what is heard and seen, must necessarily exist"). The designations (ming 名) of all matters have therefore to be adopted to reality (shi 实), and not vice versa. His logic goes so far that Mozi says that because ghosts and spirits can be seen and heard, they really exist. Politics has to make use of this circumstance by making use of facts (shi 事) and real conditions (shi 实) to bring profit (li 利) to the people and the state.
Although in the field of morality and ethics, Confucianism and Mohism have common features, there are also many differences making them adherents ardent adversaries. Mengzi 孟子, for example, castigates Mozi's "universal love" (jian'ai 兼爱), which is unacceptable for a Confucian who holds high social hierarchies: "All men under Heaven are equal to the Son of Heaven (i.e. the king or emperor)", says Mozi. He also vehemently rejects Confucianism in his last triple-treatise (Fei Ru 非儒 "Against the Confucians"). Yet inspite of all "revolutionary" or "socialist" ideas concerning the universality of love, Mozi does not want to change the structure of traditional society.

The main philosophical concepts of Mozi are universal love and a prohibition of offensive war. These two behaviours will bring harmony in society and prevent the strong exploiting the weak and the rich suppressing the poor. The will of Heaven, which loves mankind, has to be followed by the ruler, who likewise has to love his people (ai min 爱民) and to bring profit to his people (li min 利民). In this respect Mozi is very similar to Mengzi. The common people, as well as the ruler, have to obey the will of Heaven (shun tian zhi 顺天意).

Ghosts and spirits will likewise, as Mozi thinks, retribute good and evil doing (shang xian er fa bao 赏贤而罚暴 "reward the worthies, but punish the cruel"). The ruler has to understand the will of his subjects, and the subjects have to comply with the ruler. The ruler of a state has therefore to make use of the most worthy and competent persons from among the people to support him in government, even peasants and labourers. The last point is also similar to Confucian thinking. A very important point in Mozi's thinking is economical behaviour. Burials have to be austere and simple, quite contrary to Confucians who invest a lot to express their filial piety to the deceased. At the court, luxury and prodigity should be avoided. Mozi thus is against music. This is also the opposite of Confucian thought according to which music is in integral part of rituals.

During the Warring Stats period Mohist thought was very widespread, and Mozi's disciples represented an earnest competitor for Confucians like Mengzi. The most important Mohist philosophers are Qin Huali 禽滑厘, Xianzi Shuo 县子硕, Gongshang Guo 公尚过, Chanzi 缠子, Tianqiuzi 田俅子, Suichaozi 随巢子, and Hufeizi 胡非子. Some of them taught in the eastern states of Qi and Song, some in the southern states of Chu and Yue, but there were also some Mohist philosophers advising the rulers of the "newcomer" Qin 秦 in the west. The Mohist philosophers were known for their austerity and seriousness, and some leaders among them were regarded like generals to which the soliders obeyed even in the fiercest battle.