Tai Chên 戴震 (T. 慎修 H. 東原, 杲谿, Jan. 19, 1724-1777, July 1, scholar and philosopher, was a native of Hsiu-ning, Anhwei. It is said that he was unable to talk until he was ten (sui), and only then began to read. He was taught the Classics, which, after a few years, he could repeat from memory. But having a very inquisitive mind, he would not accept unquestioningly what he was told were the meanings of the words in the Classics, but tried to verify them for himself. His family was poor but he managed to acquire extensive knowledge by borrowing books from well-to-do neighbors. In the years 1740-42 he was in Nan-fêng, Kiangsi, where his father was a cloth merchant. When be was twenty sui (1742) he returned home and studied in the family of a wealthy scholar, Wang Wu-fêng 汪梧鳳 (T. 在湘 H. 溪江 1728-1772, Feb. 1), of Hui-chou, Anhwei. There was then living in Wang's home an elderly scholar, Chiang Yung 江永慎 (T. 修, 1681-1762), with whom he studied mathematics, phonology and the Record of Rites. Among the friends who studied with him at this time were Ch'êng Yao-t'ien 程瑤田 (T. 易疇, 1725-1814) and chin Pang (see under Têng Shih-ju).
In 1744 Tai Chên completed his first work, entitled 策算
While pressing a lawsuit against a clansman who had appropriated land which belonged to the entire clan, Tai Chên was threatened by the offender who happened to be both influential and a friend of the magistrate. Hence in 1754 he took refuge in Peking where he made the acquaintance of Ch'ien Ta-hsin [q.v.] on whose recommendation he was engaged by Ch'in Hui-t'ien [q.v.] to assist in compiling the latter's Wu-li t'ung-k'ao. Later he was taken into the circle of several young scholars, all of whom in time became famous, namely Chi Yün, Chu Yin, Wang Ch'ang, Lu Wên-ch'ao, and Wang Ming-shêng [qq.v. ]. In 1755 he was engaged as tutor in the family of Chi Yün who in that year sponsored the printing of his K'ao-kung chi t'u chu. In 1756 he taught, in the home of Wang An-kuo, the latter's son, Wang Nien-sun [qq.v. ], who likewise became a great scholar. Late in 1757 he went to Yangchow where for several years he was in the employ of Lu Chien-tsêng [q.v.] . During this sojourn in the south he met Hui Tung [q.v.] , Shên Ta-ch'êng (see under Wu Ching-tzŭ), and other scholars of the School of Han Learning (see under Ku Yen-wu).
In 1762 Tai Chên became a chü-jên and during the following year lived for some months in Peking. There he gave several lectures which were attended by Tuan Yü-ts'ai [q.v.] who in 1766 formally became his disciple. In this year, too, he taught in the home of Ch'iu Yüeh-hsiu [q.v.]. The following year, through the help of a friend, he gained access to the library of the Hanlin Academy where he took note of some rare works in the encyclopaedia, Yung-lo ta-tien  (see under Chu I'ün). In 1768 he was invited by Governor-general Fang Kuan-ch'êng [q.v.] to Paoting, Chihli, to complete the compilation of a work begun by Chao I-ch'ing and continued by Yü<> Hsiao-k'o [qq.v. ] on the waterways of Chihli province, entitled 志隸河渠水利書Chih-li ho-ch'ü<> shui-li shu. His contribution to it seems not to have been very great, for he was occupied with it less than a year. The Governor-general died in September of that year, and because his successor did not pay to Tai due respect we are told that he resigned and left the work unfinished. The manuscript was utilized by a man who published it under his own name, without mentioning the previous labors of Chao, Yü, or Tai (see under Chao I-ch'ing).
In 1769 Tai Chên took the metropolitan examination in Peking, but failed after two earlier (1763, 1766) unsuccessful attempts. Thereupon he went to Taiyuan, Shansi, where Chu Kuei [q.v.] was serving as financial commissioner. Later in that year (1769) he was engaged by Sun Ho-hsiang 孫和相 (T. 調鼎, 越薪), prefect of Fên-chou-fu, to edit the history of that prefecture, Fên-chou fu-chih, 34 chüan, which was completed by Sun late in 1770 and printed in 1771. In the meantime Tai left Shansi to take the metropolitan examination held (1770) in Peking; but, failing for the fourth time to become a chin-shih, he returned to Shansi in 1771 to assist the magistrate of Fên-yang in editing the history of that district, a work completed and printed in 1772, under the title Fên-yang hsien-chih, 14 chüan. Before it was completed he again (1772) went to Peking to take the metropolitan examination, but failed once more. ;Late in 1772 he went to Chin-hua, Chekiang, where he had charge of the local Academy.
While thus engaged, Tai received in the summer of 1773 an imperial mandate to serve in Peking as one of the compilers of the Imperial Manuscript Library, Ssŭ-k'u ch'üan-shu (see under Chi Yün). Earlier in that year many officials had been appointed compilers of this project, and now five others, including Tai, were summoned in special recognition of their scholarly achievements. Three of them, Shao Chin-han, Chou Yung-nien, and Yü<> Chi [qq.v.], had already become chin-shih, but the other two, Tai Chên and Yang Ch'ang-lin 楊昌霖 (T. 際時 H. 簡齋), had only the rank of chü-jên.
Tai reached Peking in September 1773 and, together with his four colleagues, began to edit rare works which they extracted from the Yung-lo ta-tien. As a sample of the studies they had made, there was submitted to Emperor Kao-tsung, in October or November of the following year, a copy of the ancient work on waterways, Shui-ching chu (see under Chao I-ch'ing), said to have been collated by Tai Chên on the basis of a superior and hitherto unused text in the Yung-lo ta-tien. The Emperor wrote a poem in praise of Tai's achievement and ordered the text to be printed in the official collectanea, Wu-ying tien chu-chên pan ts'ung-shu (see under Chin Chien). A long controversy has since taken place on the question whether Tai ever utilized the text in the Yung-lo ta-tien as reported, and the opinion seems now to be unanimous that he did not. Chang Mu [q.v.], as early as 1841, compared Tai's text with the one in the encyclopaedia, and found no evidence to show that he had made use of that work. Modern scholars, having at their disposal the Yung-lo ta-tien text which was reproduced photographically in 1935, and being thus enabled to make a detailed comparison, have come to the same conclusion. They find, moreover, that in preparing his text of the Shui-ching chu Tai drew heavily on a then unpublished collation of the same work, made by Chao I-ch'ing twenty years earlier (see under Chao). Letters written by Yü<> Min-chung [q.v.] in August and September 1774 make it plain that Tai's text was then a subject of heated criticism, in particular from Li Yu-t'ang (see under Li Fu), an associate director of the Ssŭ-k'u ch'üan-shu. They state also that a second collation of the Shui-ching chu was decided upon in the hope of settling the controversy. On October 5 Li was suddenly transferred from the capital to a relatively unimportant educational commissionership in Chekiang and, late in 1777, was permanently cashiered for being involved in the case of Wang Hsi-hou [q.v.] . Whether Li was sent qway from Peking to prevent his disclosing to the Emperor irregularities in the Ssŭ-k'u project in general, or the controversy that was raging concerning Tai's part in the Shui-ching chu text in particular, is a matter for conjecture. It seems certain, however, that after the editors had induced the Emperor to give high praise to Tai's effort, it was impossible for them to submit to the throne a better collated text without impugning their judgment and incurring severe penalties. Consequently it was to their interest, as it was to the interest of Tai himself, to maintain silence.
Like a few other scholars of his time (see under Lo Shih-lin), Tai Chên was interested in the  recovery of old works on mathematics. Ten such works, edited by officials of the Sung period for use as text-books, had been printed in 1084, under the collective title 算經十書Suan-ching shih-shu. Early in the fifteenth century these works had been copied into the Yung-lo ta-tien, but subsequently became very rare. Mao I [q.v.] spent many years searching for them and in 1684 discovered seven, of which he published several copies traced in facsimile from Sung editions. Probably unaware of Mao I's labors, Tai Chên recovered (1774-76) six of the ten items from the Yung-lo ta-tien which, together with a seventh collated by him, were printed in the Wu-ying tien chu-chên pan ts'ung-shu. In the meantime Kung Chi-han (see under Shao Chin-han), who possessed a set of Mao I's traced copies, combined them with Tai's collated texts and thus gathered nine of the original ten works of 1084, which he printed under the original title Suan-ching shih-shu. To this K'ung added one ancient mathematical treatise not among the original ten; and two works by Tai--the aforementioned Ts'e-suan ; and a work on the measurement of the circle, entitled 勾股割圜記 Kou-ku ko-yüan chi, 3 chüan (first printed in 1755). In addition to these works Tai recovered several other rare items from the Yung-lo ta-tien, among them two Sung studies about the Decorum Ritual. While thus working on various phases of the Ssŭ-k'u project, he once again took the metropolitan examination (1775), and although lie failed, he was, by a special decree, allowed to become a chin-shih and was appointed a bachelor in the Hanlin Academy. He continued to work on the Ssŭ-k'u project until his death, in Peking, two years later, in the home of a friend.
Tai Chên wrote or edited some fifty works of which thirty-five have been printed and are extant. About fifteen of these were printed during his lifetime, among them the two above-named local histories which he helped to edit, and ten works he edited for the Ssŭ-k'u ch'üan-shu. After his death, K'ung Chi-han printed (ca. 1777-79) a collection of fifteen items under the title 戴氏遺書Tai-shih i-shu which included twelve items not previously printed. In the nineteenth century four more of his works were printed in various collectanea. In 1936 there appeared a more complete edition of Tai's collected works, entitled 戴東原先生全集Tai Tung-yüan hsien-shêng ch'üan-chi. It constitutes the sixth series of the Anhwei ts'ung-shu, and contains, in addition to eighteen reprints, the following items: four works reproduced from hitherto unpublished manuscripts; some reproductions in facsimile of his handwriting; biographical sketches; a nien-p'u by Tuan Yü-ts'ai; and a bibliography of his writings.
Tai Chên made some contributions to the study of phonology, a subject which had been revived by Ku Yen-wu [q.v.] about a century earlier. He had studied the subject with Chiang Yung, discussed it with Tuan Yü-ts'ai, and left two works on it, entitled, 聲類表 Shêng lei piao, 9 chüan, printed in 1777 shortly before his death, and 聲韻考Shêng yun k'ao, 4 chüan, printed by K'ung Chi-han. The former is his classification of ancient pronunciations; and the latter represents his views on various aspects of the subject, including a critical review of Ku Yen-wu's works. He also annotated the ancient dictionary of dialects, known as Fang-yen (see under Ch'ien Ta-chao), his edition of this work being entitled Fang-yen chu shu-chêng (注疏證), 13 chüan. A manuscript copy of his unfinished supplements to the Fang-yen, entitled Hsü (續) Fang-yen, was reproduced in 1936 in the Anhwei ts'ung-shu. Also reproduced in this collectanea are a manuscript copy of his notes on the study of the Classics, entitled 經考附錄Ching-k'ao fu-lu, 7 chüan, and 3 chüan of the manuscript of the aforementioned Ch'ü<> Yüan fu chu. ;The main part of his notes on the Classics, Ching-k'ao, 5 chüan, had been previously published in the Hsü-chai ts'ung-shu (see under Chiao Hsün). A collection of his short articles in prose were printed by Kung Chi-han under the title Tai Tung-yüan chi (集), 10 chüan, being re-edited and supplemented by Tuan Yü-ts'ai in a second edition of 12 chüan, printed in 1792.
Tai Chên's most important contributions were, however, in the field of philosophy; he became, in fact, the greatest of the few philosophic thinkers whom China produced in the Ch'ing period. His philosophical views are embodied chiefly in two treatises: one, entitled 原善Yüan-shan, 3 chüan, written in its present form in 1776; the other 孟子字義疏證 Mêng-tzu tzu-i shu-chêng, 3 chüan, first composed in 1769-72, under the title 緒言Hsü-yen, but edited under its present title shortly before his death. The text, bearing the title Hsü-yen, appears in the Yüeh-ya t'ang ts'ung-shu (see under Wu Ch'ung-yüeh).
From Sung times onward the dominant philosophy of China had been a dualistic rationalism which was supposed by a long line of sponsors, official and private, to be firmly grounded on the Classics, but which the textual critics of the seventeenth century declared to be highly  colored by views derived from Buddhism and Taoism. This Sung philosophy maintained its hold throughout the Ming period because it had the patronage of a powerful bureaucracy and at the same time offered to the individual a subjective emotional release from extreme autocratic rule. According to the Sung world view, the universe has as its constituent elements: (1) ch'i 氣, ether, the primordial element, physical and psychical, of which the universe is made, and (2) li 理, the reason, principle, or law which inheres in all things and which every human being possesses from birth. Man therefore has a dual nature (性) : a material one derived from ch'i which is responsible for his passions and feelings and evil propensities, and a spiritual endowment, li, which he derives from Heaven and which is basically good. The aim of education is to free man from the less desirable impulses and help him to recover the principle, the law, or the reason, which he has at birth, but which is often beclouded by extraneous influences. One way to recover this li is by the exercise of quiet meditation-techniques which the seventeenth century thinkers perceived had been derived in part from Buddhism. Another method is by systematically lessening or suppressing the desires, as advocated, for different reasons, by both the Taoists and Buddhists.
This doctrine of the Sung philosophers, that li is Heaven-imparted and lodged in man, gave to their teachings a subjective approach which they then saw no way to overcome, but which some teachers stressed less than others. The school of Wang Yang-ming (see under Chang Li-hsiang) went so far as almost to give up the search for knowledge from without, placing reliance almost wholly on inward techniques of meditation and introspection. The school founded by the Ch'êng brothers and Chu Hsi (see under Hu Wei) talked much about pushing investigations to the limit to find the reasons or principles in things but, lacking the techniques of hypothesis and verification which alone make experimentation fruitful, the proponents of this school, too, gradually turned from the study of 'things' in the outer world, to 'things' recorded in the literary heritage of the nation.
The inadequacy of this subjective and literary approach was brought forcibly home to the thinkers of the seventeenth century but, with the exception of Yen Yüan and Li Kung [qq.v. ], none of them attempted to discredit it, as Tai Chên did in the eighteenth century, on purely philosophical grounds. The method of attack employed by the seventeenth century thinkers was historical, philological and literary. They attempted to prove on textual grounds that the Sung cosmology was not ancient, that some of the texts on which it was based were late or spurious, and that the conclusions reached were often erroneous and purely subjective (see Hu Wei, Yen Jo-chü, Ku Yen-wu and Huang Tsung-hsi). This type of textual study was called Han-hsüeh 漢學 and the men who practiced it were said to belong to the Han-hsüeh p'ai (派), or School of Han Learning, because they strove to base their conclusions on texts older than the Sung-namely, those of the Han period.
Tai Chên inherited from his predecessors all the approved techniques of this school and, as already stated, applied them with rigorous exactness to the study of the laws of phonetic changes, etymology, textual criticism, mathematics and astronomy. He went further than his predecessors, however, for he had the conviction that these studies were not ends in themselves but must be used to develop a new philosophy whose aim should be the betterment of society. For him, the supreme use of the Classics is the truth they convey; and to display those truths he was as ready to go beyond "Han Learning" as his predecessors had gone beyond "Sung Learning."
In place of the old Sung dualism Tai Chên propounded a rationalistic monism of a type foreshadowed, to be sure, in the pragmatic writings of Yen Yüan and Li Kung, but never before erected into a philosophy. He boldly thrust aside the concept of li as a Heaven-sent entity, lodged in the mind, and took the outright materialistic position that ch'i alone is sufficient to account for all phenomena--not only the basic instincts and oft-condemned emotions of man, but all the highest manifestations of man's nature. Chu Hsi had identified li with tao 道, regarding them both superior to matter. But Tai, basing himself on certain passages in the Classics of Changes, interpreted tao as the activity of nature as shown in the interaction of Yin and Yang and the Five Elements. In the natural world it displays continuous change, resulting in the unending production and reproduction of life; but in man it manifests itself in the relations that men have to one another. Everything produced in this process has its own structure and this internal structure is what Tai Chên designates li. He found from his philological studies--as Li Kung and Ch'êng T'ing-tso (see under Yen Yüan) had before him--that the word li meant originally the texture or fiber in things, like the  markings in a piece of jade or the grain in wood. The mind, though a physical organ, is capable of differentiating the li, the principle or characteristic features of things; but to do so it must "lean on nothing but the facts" (空所依傍). These principles cannot be adequately revealed by introspection or meditation; nor will they come to man in a flash of "sudden enlightenment" as the Sung philosophers had maintained. They can be known only bY"wide learning, careful investigation, exact thinking, clear reasoning, and sincere conduct." There are, in short, dependable laws and principles in things which can be ascertained and predicted with reasonable certainty. Reason is not something superimposed by Heaven on man's physical nature; it is exemplified in every manifestation of his being, even in the so-called baser emotions.
Tai Chên held that the social consequences of regarding li as a Heaven-sent entity, and of the desires as essentially evil, had worked a great harm on China. He therefore reserved for these concepts his most vehement denunciation. He did, of course, recognize that the thought of li as present in even the humblest man, had had at times a truly salutary influence-enhancing the dignity of the commonest man, giving him in effect a higher law to which he could appeal when dispassionate analysis failed to win for him freedom from injustice and oppression. But an appeal as subjective as this, had evil consequences as well. Tai Chên declared that no man's private opinion should be called li, for it is a word which "should never be used lightly". One can discern here intimations of the modern view: that scientific proof is not private, but public; that facts are things to which all men can point to equally, and not things to which one man points alone. If li is to be interpreted only by the intuitions of the neart, and not by reference to the facts of the case, what will prevent the powerful, the eloquent, or the corrupt from imposing their private ideas of li on the weak, the untutored and the innocent? Li o interpreted, said Tai, is "no li at all." It then becomes, as it often did become in actual practice, a bludgeon need by the powerful and the unscrupulous to enforce their private ends. Li is the internal structure or system in things, and this it is the business of the mind to discover, unclouded by its own prejudices and undeceived by the prejudices of others.
The Sung practice of relating the desires to ch'i or matter, and so giving to them an inferior status, and the teaching that the desires must be minimized or suppressed, were both equally objectionable to Tai Chên. In his opinion, the ideal society is one in which the natural desires and feelings can be freely expressed. He believed that the ancients ruled by giving scope to men's desires but, as time went on, one natural impulse after another was branded as vulgar or seductive, until the people hardly knew what standards to accept. ;He insisted that even the great qualities of fellow-feeling, righteousness, decorum and wisdom are simply extensions of the fundamental instincts of food and sex or the natural urge to preserve life and to postpone death, and that they are not to be sought apart from these urges. They are, in fact, manifestations of the tao which, as stated above, he identified with the endless process of change and activity. "Everything that has breath and intelligence", said he, "must by its very nature have desires." Virtue is therefore not the absence of desires, but their orderly fulfilment and expression. The attempt to lessen or repress them results, in his view, in hypocrisy, injustice and innumerable other social ills.
Perhaps the only contemporaries of Tai Chên who can be said to have grasped the import of his teachings were Hung Pang 洪榜 (T. 汝登, H. 初堂 1745-1779) and Chang Hsüeh-ch'êng [q.v.]. Hung wrote a biography of Tai in which he described the essentials of his philosophy, but he died young and thus his influence was slight. Though Chang appreciated Tai's merits, he took offense, as did others, at his attacks on the time-honored doctrines of Chu Hsi. Tuan Yü-ts'ai revered him as a teacher but, being almost devoid of philosophical interests, could not advance his master's views. Ling T'ing-k'an and Juan Yüan[qq.v.] carried on Tai's thought in part, but failed to stress certain essentials, with the result that, after their time, Tai's views ceased to have a vogue in China. Under the preSsŭre of Western aggression and internal disorder a need for the consolations of Sung philosophy again asserted itself; and it was not until the opening of this century, when Tai's nearness to Western thought became apparent, that his really important place in the history of philosophy has been appreciated. [See Note by Hu Shih on Tai Chên, Chao I-ch'ing and Ch'uan Tsu-wang, p. 970. Ed.]
[ Anhwei ts'ung-shu, sixth series; Hu Shih, "The Philosophy of Tai Tung-yüan" (in Chinese), Kuo-hsüeh chi-k'an (Jour. of Sinological Studies), vol. ü, no. 1, Dec. 1925;idem., "The Philosopher, Ch'êng T'ing-tso, of the School of Yen Yüan" (in Chinese), Kuo-hsüeh chi-k'an, vol. 5, no. 3, 1935; Freeman, Mansfield, "The Philosophy of Tai  Tung-yüan", Jour. N. China. Br. Royal Asiatic Soc., vol. 64 (1933); Ch'ien Mu, Chung-kuo chin san-pai nien hsüeh-shu shih (see bibl. under Mao Ch'i-ling), vol. 1, pp. 306-79; Fung Yu-lan, History of Chinese Philosophy (1934, Chinese ed.), pp. 994-1009;Ch'ing ju-hsüeh-shu t'ao-lun chi (see bibl. under Sun I-jang), 1st series, pp. 25-67; Chang Tê-k'un, "Did Tai Plagiarize Chao in the Shui-ching chu ?" (in Chinese), Yenching Journal of Chinese Studies, no. 19, June 1936; Mêng Sen, "The So-called Textual Emendations in Tai Chên's Edition of the Shui-ching chu ", Kuo-hsüeh chi-k'an, vol. 6, no. 2, 1936.]