al-Muqaddima and the rest of Kitāb al-ʻIbar
Kitāb al-ʻIbar, (full title: Kitāb al-ʻIbar wa-Dīwān al-Mubtadaʼ wa-l-Khabar fī Taʼrīkh al-ʻArab wa-l-Barbar wa-Man ʻĀṣarahum min Dhawī ash-Shaʼn al-Akbār: "Book of Lessons, Record of Beginnings and Events in the History of the Arabs and the Berbers and Their Powerful Contemporaries"); begun as a history of the Berbers and expanded to a universal history in seven books.
Book 1; Al-Muqaddima ('The Introduction'), a socio-economic-geographical universal history of empires, and the best known of his works.
Books 2–5; World History up to the author's own time.
Books 6–7; Historiography of the Berbers and the Maghreb. Khaldun departs from the classical style of Arab historians by synthesising multiple, sometimes contradictory, sources without citations. He reproduces some errors originating probably from his 14th-century Fez source, the work Rawḍ al-Qirṭās by Ibn Abi Zar, yet Al-'Ibar remains an invaluable source of Berber history.
Concerning the discipline of sociology, he described the dichotomy of sedentary life versus nomadic life as well as the inevitable loss of power that occurs when warriors conquer a city. Al-Sakhāwī describes Kitāb al-ʿIbar as Ibn Khaldūn’s major historical work and notes that it was prefaced with a lengthy introduction addressing civilization (ʿumrān), kingship, livelihood, and the sciences. Encyclopaedia Britannica likewise highlights the Muqaddimah as his best-known work and a landmark statement of his philosophy of history. According to the Arab scholar Sati' al-Husri, the Muqaddimah may be read as a sociological work. The work is based around Ibn Khaldun's central concept of aṣabiyyah, translated as "group cohesiveness" or "solidarity". This social cohesion arises spontaneously in tribes and other small kinship groups; it can be intensified and enlarged by a religious ideology. Ibn Khaldun's analysis looks at how this cohesion carries groups to power but contains within itself the seeds – psychological, sociological, economic, political – of the group's downfall, to be replaced by a new group, dynasty or empire bound by a stronger (or at least younger and more vigorous) cohesion. Some of Ibn Khaldun's views, particularly those concerning the Zanj people of sub-Saharan Africa, have been cited as racist. According to the scholar Abdelmajid Hannoum, Ibn Khaldun's description of the distinctions between Berbers and Arabs were misinterpreted by the translator William McGuckin de Slane, who wrongly inserted a "racial ideology that sets Arabs and Berbers apart and in opposition" into his translation of part of`Ibar translated under the title Histoire des Berbères.
Perhaps the most frequently cited observation drawn from Ibn Khaldūn's work is the notion that when a society becomes a great civilization, its high point is followed by a period of decay. This means that the next cohesive group that conquers the diminished civilization is, by comparison, a group of barbarians. Once the barbarians solidify their control over the conquered society, however, they become attracted to its more refined aspects, such as literacy and arts, and either assimilate into or appropriate such cultural practices. Then, eventually, the former barbarians will be conquered by a new set of barbarians, who will repeat the process.
Georgetown University Professor Ibrahim Oweiss, an economist and historian, argues that Ibn Khaldun was a major forerunner of modern economists and, in particular, originated the labor theory of value long before better known proponents such as Adam Smith and David Ricardo, although Khaldun did not refer to it as either a labor theory of value or theory.
Ibn Khaldun also called for the creation of a science to explain society and went on to outline these ideas in his major work, the Muqaddimah, which states that "Civilization and its well-being, as well as business prosperity, depend on productivity and people's efforts in all directions in their own interest and profit".
Ibn Khaldun diverged from norms that Muslim historians followed and rejected their focus on the credibility of the transmitter and focused instead on the validity of the stories and encouraged critical thinking.
Ibn Khaldun also outlines early theories of division of labor, taxes, scarcity, and economic growth.
He argued that poverty was a result of the destruction of morality and human values. He also looked at what factors contribute to wealth, such as consumption, government, and investment. Khaldun also argued that poverty was not necessarily a result of poor financial decision-making but of external consequences and therefore the government should be involved in alleviating poverty. Researchers from Malaysia's Insaniah University College and Indonesia's Tazkia University College of Islamic Economics created a dynamics model based upon Ibn Khaldun's writings to measure poverty in the Muslim nations of South Asia and Southeast Asia.
Ibn Khaldun also believed that the currency of an Islamic monetary system should have intrinsic value and therefore be made of gold and silver (such as the dirham). He emphasized that the weight and purity of these coins should be strictly followed: the weight of one dinar should be one mithqal (the weight of 72 grains of barley, roughly 4.25 grams) and the weight of 7 dinar should be equal to weight of 10 dirhams (7/10 of a mithqal or 2.96 grams).
Ibn Khaldun's writings regarding the division of labor are often compared to Adam Smith's writings on the topic.
The individual being cannot by himself obtain all the necessities of life. All human beings must co-operate to that end in their civilization. But what is obtained by the cooperation of a group of human beings satisfies the need of a number many times greater than themselves. For instance, no one by himself can obtain the share of the wheat he needs for food. But when six or ten persons, including a smith and a carpenter to make the tools, and others who are in charge of the oxen, the ploughing of, the harvesting of the ripe grain, and all other agricultural activities, undertake to obtain their food and work toward that purpose either
separately or collectively and thus obtain through their labour a certain amount of food, that amount will be food for a number of people many times their own. The combined labour produces more than the needs and necessities of the workers (Ibn Khaldun 1958, vol. II 271–272)
In every other art and manufacture, the effects of the division of labour are similar to what they are in this very trifling one [pin production]; though, in many of them, the labour can either be so much subdivided, nor reduced to so great a simplicity of operation. The division of labour, however, so far as it can be introduced, occasions, in every art, a proportionable increase of the productive powers of labour (Smith 1976a, vol. I, 13–24)
Both Ibn Khaldun and Smith shared the idea that the division of labor is fundamental to economic growth, however, the motivations and context for such division differed between them. For Ibn Khaldun, asabiyyah or social solidarity was the underlying motive and context behind the division of labor; for Smith it was self-interest and the market economy.
