This paper considers the factors the allowed for the birth and facilitated the subsequent development of the equity side and the finance (or debt) side of the Islamic capital markets. The equity side of the Islamic capital markets began in 1998 with the issuance (after five years of debate) of a fatwa to Dow Jones Islamic Market Indexes in respect of the first equity indexes of Shari'ah-compliant equities. That fatwa institutionalized permissible variance or permissible impurity concepts relating to equity investments in entities that (a) had some degree of impermissible interest income or interest expense or (b) conducted some impermissible business activities (such as those involving activities relating to alcohol or pork for human consumption, interest-based financing, non-takaful insurance, pornography, prostitution or weapons, among other matters). That fatwa also institutionalized purification or cleansing techniques to address impermissible income actually received (such as from interest on investments or earnings from allowed impermissible business activities). The paper surveys the application of these variance and purification concepts and principles in areas of finance and investment other than non-controlling equity investments: for example in private equity, real estate and project finance. The finance side of the Islamic capital markets began in the period of 2001-2003 with the first sukuk issuances from the Middle East (there had been earlier issuances in Malaysia) [...]