The Balance: The Core Mental Model of the Islamic Science of Weights


by Mohammed Abattouy

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This article includes the recent work by Professor Abattouy and his co-workers. The work has revealed the enormous wealth of Islamic literature on the science of weights. Their findings established that there is much larger account than usually assumed in history of science.

Summarised extracts from a full article:
The Islamic Science of Weights and Balances: A Refoundation of Mechanics Deeply Rooted in the Social Context of the Islamic Civilisation by Prof. Mohammed Abattouy

The balance is an instrument of enormous importance in all aspects of life, from everyday dealings to the precession of science and technology. In early Islamic times, this familiar instrument was the subject of an extensive scientific and technical debate of which dozens of treatises on different aspects of its theory, construction, and use are the precious remains. In the Islamic scientific tradition, different sorts of balances were the object of extensive enquiry, including the normal equal-armed balance (called mizan, tayyar, and shahin), the steelyard (called qarastun, qaffan, and qabban) and sophisticated balances for weighing absolute and specific weights of substances.

Several drawings of balances are preserved in Arabic manuscripts, such as those of Al-Khazini, Al-Hariri, and Al-Qazwini. Further, some specimens of the ancient balances survived and are presently kept in different museums around the world. For instance, a balance is preserved in the National Museum in Kuwait (LNS 65M). Built in Iran in the 10th century, it is made of steel and bears marks on its beam. Its dimensions (height: 11.5 cm, length: 15.6 cm) show that it was used for weighing small quantities. The second, dating probably from the 12th century, is kept in the Science Museum in London (accession number Inv. 1935-457). This balance came to the Science Museum in 1935 from University College London, together with a large selection of archaeological material consisting of ancient weights and measures collected from the Near East by Flinders Petrie. A scale of silver is inlaid along its 2.37m long, wrought-iron beam. It bears two suspending elements, and corresponding calibrations: one ranging from zero to 900 ratl-s (1 ratl is approximately one pound); the other ranging from 900 to 1820 ratl-s.

The interest in the balance in Islamic scientific learning was culturally nurtured by its role as a symbol of good morals and justice. The Qur’an and the Hadith appealed extensively to a strict observance of fair and accurate weighing practices with the balance. Considered the tongue of justice and a direct gift of God, the balance was made a pillar of the right society and a tool of good governance. These principles were recorded explicitly in several treatises on the balance, such as the introduction to Kitab mizan al-Hikma (the book of the balance of wisdom) by al-Khazini, where the balance is qualified as “the tongue of justice and the article of mediation.” Furthermore, it was counted as a fundamental factor of justice, on the same level with “the glorious Book of God,” and “the guided leaders and established savants.” emergence of Arabic mechanics is an early achievement in the scientific tradition of Islam. Actually, already in the mid-9th century, and in close connection with the translation of Greek texts into Arabic, treatises on different aspects of the mechanical arts were composed in Arabic, but with a marked focus on balances and weights. These writings, composed by scientists as well as by mechanicians and skilful artisans, gave birth to a scientific tradition with theoretical and practical aspects, debating mathematical and physical problems, and involving questions relevant to both the construction of instruments and the social context of their use. Some of these Arabic treatises were translated into Latin in the 12th century and influenced the European science of weights.

The corpus of the Arabic science of weights covers the entire temporal extent of scientific activity in medieval Islam and beyond, until the 19th century. The reasons for such an abundance of literature on the problems of weighing can be explained only by contextual factors. In fact, the development of the science of weights as an autonomous branch of science was triggered by the eminent importance of balances for commercial purposes. In a vast empire with lively commerce between culturally and economically fairly autonomous regions, more and more sophisticated balances were, in the absence of standardization, key instruments governing the exchange of currencies and goods, such as precious metals and stones. It is therefore no surprise that Muslim scholars produced numerous treatises specifically dealing with balances and weights, explaining their theory, construction and use. This literature culminated in the compilation by Abd ar-Rahman al-Khazini, around 1120, of Kitab mizan al-hikma, an encyclopedia of mechanics dedicated to the description of an ideal balance conceived as a universal tool of a science at the service of commerce, the so-called ‘balance of wisdom.’ This was capable of measuring absolute and specific weights of solids and liquids, calculating exchange rates of currencies, and determining time.

Recent work by Professor Abattouy has revealed the enormous wealth of Islamic literature on the science of weights. Surprisingly, his findings established that there is much larger account than usually assumed in history of science. Up to now more than thirty treatises dating from the 9th through the 19th centuries have been identified which deal with balances and weights in the narrow sense. The majority of these treatises has never before been edited or studied, and only exists in one or more manuscript copies. Some important manuscripts have been discovered or rediscovered even in the course of the research activities conducted by Professor Abattouy.

Image Sources

Image (top): Seyyed Hossein Nasr, Islamic Science. An Illustrated Study, Kent 1976.

Image (bottom): Seyyed Hossein Nasr, Islamic Science. An Illustrated Study, Kent 1976.