Riba (interest, usury) is primarily an economic issue in view of the fact that all religions and mythologies have prohibited, restricted, discouraged, disliked, or degraded Riba in one way or the other since the inception of human interaction. All three major revealed (Ilhami) religions i.e., Islam, Christianity, and Judaism have strongly condemned and prohibited Riba in its original versions. Later, the clerics of Jews and Christian Church abandoned the prohibition of Riba (interest, usury) that led the mankind into the economic anarchy of the present era.
Islam - the most modern revealed religion is still upholding the righteous prohibition of Riba although not in practice in any of the Islamic country at governmental level but there is immense enthusiasm for Riba-Free financial system in Muslims. The western economists have discussed the issue at large in the twentieth century and many of them are also of the view that the religious prohibition should be brought back into the conscious of the people.
As long as Riba prohibition was enforced with religious zeal, people were prosperous and the wealth distribution was not abnormal as it is today, and obviously there was not much debate on the subject but since the Riba was made legal by Judo-Christian amendments in the divine law - its destructive fallouts earthed at large. The debate started on Riba for its literal interpretation to economic implications.
It is very unfortunate to observe that, in this debate, some misconception in Muslims led to a widely circulated explanation of Riba that divide Riba in to two types, one from Quran (riba-al-nasiah) and the other from Sunnah (riba-al-fadl or riba-al-buyu) and interpreted these as "riba in debt" and "riba in trade" respectively, this division which actually is not the case; is a direct conflict with basic faith of Islam (please see "Present Islamic understanding and misconception about Riba" for details). No clear concept and universal definition of Riba exists, different views and explanations have created much confusion in Muslims in the understanding of Riba. Unless, it is not found that Why Riba was declared Haram (prohibited), the definition of Riba is not possible.