Tian is one of the oldest Chinese terms for the cosmos and a key concept in Chinese mythology, philosophy, and religion. During the Shang Dynasty (17th–11th centuries BCE) the Chinese called god Shangdi (上帝 "lord on high") or Di ("lord"), and during the Zhou Dynasty (11th–3rd centuries BCE) Tian "heaven; god" became synonymous with Shangdi.
In the Chinese philosophical systems of Taoism and Confucianism, Tian is often translated as "Heaven" and is mentioned in relationship to its complementary aspect of Di (地), which is most often translated as "Earth". These two aspects of Daoist cosmology are representative of the dualistic nature of Daoism. They are thought to maintain the two poles of the Three Realms of reality, with the middle realm occupied by Humanity (人 Ren).
Besides the usual 天, tian "heaven" has several graphic variants like 兲 (written with 王 "king" and 八 "8") and the Daoist coinage 靝 (with 青 "blue" and 氣 "qi", i.e., "blue sky").
The simplified chinese version is slightly different from the traditional chinese version (天). The relative lengths of the two horizontal bars are different in the two cases.
For three thousand years it has been believed that from time immemorial all Chinese revered T'ien 天, "Heaven," as the highest deity, and that this same deity was also known as Ti 帝 or Shang Ti 上帝. But the new materials that have become available in the present century, and especially the Shang inscriptions, make it evident that this was not the case. It appears rather that T'ien is not named at all in the Shang inscriptions, which instead refer with great frequency to Ti or Shang Ti. T'ien appears only with the Chou, and was apparently a Chou deity. After the conquest the Chou considered T'ien to be identical with the Shang deity Ti (or Shang Ti), much as the Romans identified the Greek Zeus with their Jupiter. (1970:493)Creel refers to the historical shift in ancient Chinese names for "god"; from Shang oracles that frequently used di and shangdi and rarely used tian to Zhou bronzes and texts that used tian more frequently than its synonym shangdi.
First, Creel analyzes all the tian and di occurrences meaning "god; gods" in Western Zhou era Chinese classic texts and bronze inscriptions. The Yi Jing "Classic of Changes" has 2 tian and 1 di; the Shi Jing "Classic of Poetry" has 140 tian and 43 di or shangdi; and the authentic portions of the Shu Jing "Classic of Documents" have 116 tian and 25 di or shangdi. His corpus of authenticated Western Zhou bronzes (1970:464–75) mention tian 91 times and di or shangdi only 4 times. Second, Creel contrasts the disparity between 175 occurrences of di or shangdi on Shang era oracle inscriptions with "at least" 26 occurrences of tian. Upon examining these 26 oracle scripts that scholars (like Guo Moruo) have identified as tian 天 "heaven; god" (1970:494–5), he rules out 8 cases in fragments where the contextual meaning is unclear. Of the remaining 18, Creel interprets 11 cases as graphic variants for da "great; large; big" (e.g., tian i shang 天邑商 for da i shang 大邑商 "great settlement Shang"), 3 as a place name, and 4 cases of oracles recording sacrifices yu tian 于天 "to/at Tian" (which could mean "to Heaven/God" or "at a place called Tian".
The Shu Jing chapter "Tang Shi" (湯誓 "Tang's Speech") illustrates how early Zhou texts used tian "heaven; god" in contexts with shangdi "god". According to tradition, Tang of Shang assembled his subjects to overthrow King Jie of Xia, the infamous last ruler of the Xia Dynasty, but they were reluctant to attack.
Having established that Tian was not a deity of the Shang people, Creel (1970:501-6) proposes a hypothesis for how it originated. Both the Shang and Zhou peoples pictographically represented da 大 as "a large or great man". The Zhou subsequently added a head on him to denote tian 天 meaning "king, kings" (cf. wang 王 "king; ruler", which had oracle graphs picturing a line under a "great person" and bronze graphs that added the top line). From "kings", tian was semantically extended to mean "dead kings; ancestral kings", who controlled "fate; providence", and ultimately a single omnipotent deity Tian "Heaven". In addition, tian named both "the heavens" (where ancestral kings and gods supposedly lived) and the visible "sky".
The Chinese philosopher Feng Youlan differentiates five different meanings of tian in early Chinese writings:
(1) A material or physical T'ien or sky, that is, the T'ien often spoken of in apposition to earth, as in the common phrase which refers to the physical universe as 'Heaven and Earth' (T'ien Ti 天地).
(2) A ruling or presiding T'ien, that is, one such as is meant in the phrase, 'Imperial Heaven Supreme Emperor' (Huang T'ien Shang Ti), in which anthropomorphic T'ien and Ti are signified.
(3) A fatalistic T'ien, equivalent to the concept of Fate (ming 命), a term applied to all those events in human life over which man himself has no control. This is the T'ien Mencius refers to when he says: "As to the accomplishment of a great deed, that is with T'ien" ([Mencius], Ib, 14).
(4) A naturalistic T'ien, that is, one equivalent to the English word Nature. This is the sort of T'ien described in the 'Discussion on T'ien' in the [Hsün Tzǔ] (ch. 17).
(5) An ethical T'ien, that is, one having a moral principle and which is the highest primordial principle of the universe. This is the sort of T'ien which the [Chung Yung] (Doctrine of the Mean) refers to in its opening sentence when it says: "What T'ien confers (on man) is called his nature." (1952:31)
The Oxford English Dictionary enters the English loanword t'ien (also tayn, tyen, tien, and tiān) "Chinese thought: Heaven; the Deity." The earliest recorded usages for these spelling variants are: 1613 Tayn, 1710 Tien, 1747 Tyen, and 1878 T'ien.
Tiān 天 reconstructions in Middle Chinese (ca. 6th–10th centuries CE) include t'ien (Bernhard Karlgren), t'iɛn (Zhou Fagao), tʰɛn > tʰian (Edwin G. Pulleyblank), and then (William H. Baxter). Reconstructions in Old Chinese (ca. 6th–3rd centuries BCE) include *t'ien (Karlgren), *t'en (Zhou), *hlin (Baxter), and *thîn (Schuessler).