<論説>南郡の建設と戦国秦の貨幣制度

Abstract

戦国期の秦国では献公が亡命先の魏国から帰国後、国の体質改善をはかり、その一環として貨幣経済を導入、銅銭の鋳行を模索する。孝公をへて恵文王二年には秦国独自の貨幣半両銭を発行、半両銭は秦国の領内に普及する。一方、白起の楚都郢の攻略、南郡の建設により黄金の流通地を領内に組み入れた結果、秦国は黄金貨幣の流通圏となり、黄金貨幣を通貨の一つに加えることになる。楚国の度量衡は鎰・両制であったところから、楚制を受け入れた秦国の黄金の衡量には鎰・両制が採り入れられた。司馬遷が秦の貨幣制度について「黄金は鎰を以て名づけ、上幣となす。銅銭は識して半両と曰い、重さは其の文の如し。下幣となす」とした記事には戦国後期から統一期にかけての秦の貨幣経済の二段階の変容が反映しているのである。

The "Treatise on the Balanced Standard" (Pingzhunshu) in the Records of the Grand Historian (Shiji) records that the monetary system of the Qin dynasty was a dual one based on gold and copper coinage, that gold was measured in units of weight known as yi, and that copper banliang coins circulated. However, the inconsistency of the system has been pointed out due to the fact that the yi unit of weight for gold did not appear in the Qin's standardized system of weights and measures. Also in regard to copper coins, the absence of a uniform standardized currency has been pointed out due to the fact that the banliang coins have been excavated chiefly from the Qin homeland of Shanxi and Sichuan. On the basis of these facts, I theorized in 1978 that the text described the Qin system during the Warring States period and not the standardized monetary system of the Qin Empire. As regards the copper coins, a recognition that banliang coins had become the established currency in the second year of the reign of King Huiwen (336 BCE) has become the scholarly consensus as a result of the report of the excavation of banliang coins together with wooden tablets of the land regulations from a Qin-era tomb in Qingchuan county, Sichuan, in 1982, but the matter of gold remained a mystery. This mystery, however, was clarified in 2001 when a Chinese numismatist pointed out that the yi was a unit of the state of Chu and that it was nearly the same weight, 250 grams, of the Qin catty, jin. Previously, as the yi had mistakenly been calculated at 320 grams and the gold coin of the Qin was 250 grams and the weight and numerical value had not corresponded, scholars claimed the description in the "Treatise on the Balanced Standard" was overly abstruse or mistaken, but with this new knowledge, it became clear that the one-jin gold coin that circulated in the Qin was actually the one-yi gold coin. Gold had from the first been prized in Qin and was employed for ornament and ritual implements, but gold coins were not utilized as currency. The use of gold coins in Qin was profoundly related to the broad-scale occupation of the heartland of the neighboring state Chu, including the capital Ying, and establishment of Nan commandery in 277 BC, when territory in which gold coins circulated came under Qin jurisdiction. The Qin state adopted the one-yi gold coins of Chu that flowed in from Nan commandery as their own currency and thus established a dual currency using them along with their own banliang coppers. Those items of the Qin Empire that could be uniformly standardized in short order -- characters, laws, weights and measures, and axle lengths -- were standardized when the realm was unified in 221 BC, but the currency and thinking of people could not be standardized immediately due to circumstances despite apparent attempts to control them when circumstances permitted. The currency was only standardized in the final year of Shihuangdi's reign, 210 BC. However, the emperor fell ill and died while on an imperial progress. Before measures to propagate the system could be taken, the empire sank into chaos and collapsed, and thus the implementation of a standardized uniform system of currency was left to the following Han dynasty. The form of the Qin currency system described by Sima Qian in the "Treatise on the Balanced Standard" was borne from the process of unification during the Warring States period and it can be termed a part of the system that failed to take root as a standardized system. Following Qin's capture of Nan commandery where gold was produced and circulated, the gold coins that flowed into the state were put to use in international politics. Gold was sent to the ministers of various states in a campaign of bribery, designed to suppress the confederation of Six Northern and Southern Kingdoms in the east, which were one by one attacked and conquered. A mere ten years after beginning the wars of unification, the realm was pacified. The establishment of Nan commandery not only brought about the addition of gold coins to the Qin monetary system but also played a dual historical role in the sense that coins from Nan commandery were used to fund the campaign of bribery.