On the other hand, was the dark ages that experienced by the western world it is inversely related to the development of science in the Islamic world. During this period was the golden age of Islam, where many Muslim scientists succeeded in giving the works of significant scientific, one of the world in development economics. Many Muslim scholars who write, research, and produce economic theories that result up to now are still relevant to be studied and applied.

Some Muslim scholars who managed to produce phenomenal work on the economic theory of them is Ibn Taymiyyah, Ibn Rushd, Ibn Khaldun, Al-Ghazali, and much more. Ibn Taymiyyah, for example, had issued a theory known as 'price volatility' or the ups and downs in market prices. He stated that: "For the ups and downs in market prices not only because of the injustice caused by a particular person or party, but also because of the short length of production period (khalq) a commodity. If production rises and demand falls, the market price will rise, on the other hand, if production falls and demand rises, the market price will come down. "The theory is if we examine more deeply involve the law of supply and demand (supply and demand) in the market , now it is recognized as a theory of irony that comes from the western world.

Another figure who managed to give a big contribution is the Ibn Rushd (Aveorrus). Roger E. Backhouse (2002), wrote a book called 'The Penguin History of Economic, which contains in it about the work produced by Ibn Rushd. He produced a theory by introducing a fourth function of money as a means of saving the purchasing power of consumers, who stressed that the money can be used at any time by consumers for buying life. Earlier, Aristotle mentions that the function of money there are three, namely: as a medium of exchange, a tool to measure value, and as a reserve for future consumption.

Ibn Rushd also denied Aristotle's theory of value for money, where its value should not change. Ibn Rushd states that the money should not be changed for two reasons, first, the money serves as a tool to measure value, then the same as Allah, the Most Estimator, he would not change, then the money as a measure of the situation should not be changed. Second, money serves as a reserve for future consumption, the change in him is not fair. From both these reasons, the actual nominal value of money must be equal to its intrinsic value.

Other experts are Ibn Khaldun's theory that produces development and social development and economic impact on the well-being. Umer Chapra (2000), states that Ibn Khaldun had to give enlightenment to the world economy, where the state's role is crucial in social development. Ibn Khaldun stressed that Sharia will not be straight if not through the state's role or authority, the state will not run well without the implementation of sharia law. State or government will not run well without the people (the Caliph). Sustainability of people will not run without the capital / assets (al maal). Property obtained from a significant development (imarat), and construction will not run without some measure of justice, and justice is one of the criteria men brought to account by Allah SWT. So, according to Ibn Khaldun in the application of sharia would not erect state without justice is based on the social and economic fields.

The next character is Al Ghazali who stated that the needs of human life consists of three primary needs (darruriyyah), secondary (hajiat), and the need for expensive (takhsiniyyat). Hierarchy of needs theory is then 'taken' by Nassau William Senior which states that human needs consist of basic needs (necessity), secondary (Decency), and tertiary needs (luxury). Al-Ghazali was also expressed about the main purpose of sharia is a problem penerepan religion or religion, life, thoughts, descent, and wealth is concerned with economic issues.

There are many other works produced by Muslim scientists to the development of economic science. The sad fact of their theories claimed came from the west, but if we examine the significance of economic theory in the western world, was first produced by a professor from the University of Glasgow, whose name was Adam Smith in his book "An Inquiry Into the Nature and Cause Of The Wealth of Nations ". The book was produced in the 18th century, which even it there are many similarities with the book 'Origin' Ibn Khaldun's work produced a few centuries earlier.

Contribution of the Islamic economic scientists is that we must make reference to keep on learning and produce significant works, both in the field of economics, and other sciences in accordance with our expertise of each. May Allah SWT make us people who thirst for knowledge and make us all closer and taqarrub Him. Amen. Allaah 'alamu bi-ashowab