As we all know, conventional financial theory based arguments justifying the existence of interest (interest) through the concept of time value of money (time value of money). In the Islamic economy, the validity of this concept has been disproved his argument with the prohibition of usury in Islam. Instead, the business activities of Islamic Economics always stressed to the mechanism for the system (profit and loss sharing). The concept of partnership is considered more appropriate and in accordance with the principles of justice are realistic.

In conventional economics, the definition often used to describe the sense time value of money is "A dollar today is worth more than a dollar in the future because a dollar today can be Invested to get a return" This understanding is certainly not accurate because each investment is always have the possibility to obtain positive results, negative, or no return. That is why in financial theory, always known risk-return relationship (in the direction of the relationship between risk and outcome). The higher the level of risk faced / borne, the greater the results you want / get, and vice versa.
According to the opinion of conventional economists, there are two things that became the foundation of the concept of time value of money, namely:

1. Presence of Inflation
Can dimisalkan: inlasi level say 10% per year. One can buy 10 bananas fried today with pay 10,000 when he bought it, but next year, with the same amount of money he only 10,000 can buy fried bananas 9. Therefore, he will ask for compensation for the loss of purchasing power of money due to inflation.

2. Preference present consumption to future consumption
Assumes zero inflation rate, so with 10,000 person can still buy 10 bananas fried today or next year. For most people, eating 10 fried bananas now more unpopular than consuming fried banana 10 next year. With this reason, although the zero inflation rate, preferably 10,000 and consumed today. Therefore, to postpone consumption, it requires compensation.

The first argument be refuted because it is incomplete condition. In every economy there is always a state of inflation and deflation. It should state the reason for the deflation becomes a negative time value of money. Say deflation rate 10% per year. Fried banana 10 days worth 10,000, but when he bought it with money next year as it can be fried plantain 11. Therefore, it would give compensation for the rising purchasing power of money due to deflation. But in reality this does not apply, only one state are accommodated by the time value of money.

Conventional Economics is also incorporated elements of uncertainty and call return as the discount rate of compensation which is more general than the term interest rate. The uncertainty of return is converted to a premium for certainty over uncertainty. Investment course there is always a possibility of getting positive returns, negative return, and no return. This is what caused uncertainty (uncertainty), but the probability of negative returns and no return is exchanged for something definite, premium for uncertainty.

This situation is rejected in the Islamic Economy, a condition al-ghunmu bi la ghurmi (Gaining responsible for return without any risk) and al-kharaj bi la dhaman (without income Gaining responsible for any expense). Actually, this situation is also rejected by the financial theory that explains the direction of the relationship between risk and return.

The same quantity of time for everybody, which is 24 hours a day, 7 days a week. But the value of time will vary from one person to than others. For example for a laborer working hour is worth 25.000, for financial managers to produce Rp.250.000, whereas for Islamic Economics expert Rp.2.500.000 appreciated.

So the factors that determine the value of time is how someone used the time. The more effective (efficiency) and efficient (right way), the higher the value of time. Effective and efficient will be profitable in the world for those who carry it out. Therefore, whoever the perpetrator, the benefit sunnatullah action in the world.

Moreover, in Islam you are looking for profits not only benefit the world but also in the hereafter. Therefore the use of time not only to effective and efficient, but he also must be based on the faith. Faith is what will bring benefits in the afterlife. Conversely, if the faith can not be profitable in the world, means that there are factors that have not obliged.

Risk of Economic and Business Fluctuations
State of an economy would fluctuate from one period to another period. A business activity would also be affected by the macroeconomic situation, which inevitably have to take into account the risk factor in business. Referring to the time value of money, conventional economics use the scale to measure the interest rate and inflation uncertainty factor. This is to mensiasati to a smaller degree of risk and obtain the desired level of profit.

Uncertainty in conventional economic thinking was based on two things. First, the uncertainty caused by several investment options with the level of risk and benefits of different expectations. Second, the uncertainty as a result of economic conditions uncertain and unpredictable. The situation is all this uncertainty is usually addressed by monetary policy through interest as the main instrument for controlling the money supply / tackle inflation.

Instrument system in anticipation of interest rate uncertainty in economic studies of Islam itself does not want its existence. However, a business activity would be influenced by macroeconomic factors of inflation. This is what makes the reasons given in addition to the value of money paid in credit by taking into account inflation. This additional money allowed for the value of the fixed and does not include usury. The amount of additive is not allowed to be determined at the start / predictable for long-term but should be in accordance with the reality that has happened.

Modern business finances are often filled with elements of speculation (gharar) and interest (usury). On the contrary, Islam was strictly prohibits these elements and using real analysis to calculate the level of benefits and risks of each business. Thus, possible benefits and disadvantages of different for the same loan amount. Islamic Economic Studies of the theory itself is still interest in micro-economic approach has not so deep and comprehensive in the areas of macroeconomic policy and monetary policy.

Sharing System as a Solution
In response to a disagreement with the theory of interest (time value of money), Economics of Islam offers a system of cooperation with the mechanism for the results (profit and loss sharing). A fairer system departs from the assumption that every effort always is the risk of both profit and loss so that both parties must be prepared to share and accept whatever happens is not just one side only of profit or loss.

In Islamic Financial Institutions, principles and mechanisms for the results applied to mudaraba and musharaka product. But unfortunately the main product of this proportion is still smaller than other products. This deficiency occurs because of socialization and understanding of public institutions has not run optimally. Public education is needed so that more information for the same perception of the institution and the community.

The idea and concept for a just outcome will be successful if executed with a consistent and professional. However, difficult to apply in the real world, because the face the uncertainty and inflation. These obstacles can be overcome with modifications as long as still within the framework of sharia. Through the Islamic system is more equitable, Islamic Financial Institutions still have a chance for economic pemberdayakan primarily on small business.