In all normative matters, the Shiite perspective is characterized by the role of Muhammad's family and the Imams as sources of guidance—either in connection with interpretations of the Quran and the model of Muhammad or independently. Moral principles are presented in different ways, sometimes reflected in binding legal prescriptions, sometimes personified in the protagonists of sacred narratives.
A prominent principle in Islamic thought that combines legal and moral aspects is referred to as 'commanding the right and forbidding the wrong'. It stipulates that Muslims should not only follow the principles of Islamic law and morality themselves, but should also make sure that others pay heed to them. Among Shiites, there are different views as to the practical implications of this principle, since they were usually not in a position of power and since the restoration of justice is only expected from the Mahdi.
The interpretation of principles of moral thought and action also depends on the significance Shiites attribute to secret knowledge. There have been notorious cases of antinomianism among extreme Shiites and medieval Ismailis that suggest that for them, the apparent meaning of the law is overruled and can be reversed by insights into its inner dimension. Within such a framework, duties such as prayer, tax, and jihad are regarded with a pragmatic attitude as measures to discipline the deficient human nature. Ismailis sometimes distinguish between rational rules, such as the prohibition of homicide, which are going to remain once the Mahdi arrives, and those that will be abolished.
Sunni polemicists criticize Shiites for their esoteric interpretation of Islamic law. In reality, the practice of Islamic law according to its inner principles remained limited to extreme Shiites. Quietist Imami scholars had found an acceptable arrangement with unjust rule, and even in Fatimid Egypt there was no space for antinomianism. As was often the case with such movements, the political success required a reinterpretation of the initial doctrines.
Twelver Shiite law does not differ more from Sunni law than one of the Sunni legal schools from another one. Shiite law uses the same two textual sources—the Quran and the traditions of the Prophet (even though they are handed down by different chains of transmitters). Parallel to the Sunni schools, which are named after scholars, the Imami Shiite legal school is referred to as Jafari after the sixth Imam, Jafar al-Sadiq (d. 765). Many decisions and principles are attributed to the sixth Imam, who probably enjoys the highest authority as a scholar among the Imams, although the authenticity is questionable. Shiite law under the Ismaili Fatimids followed a different course. A very influential text here was the legal compendium The Pillars of Islam written by Qadi al-Numan.
Shiite legal scholars also use the same set of methods as their Sunni colleagues. Both, for example, addressed the challenge of authenticating prophetic traditions by examining the reliability of the transmitters and whether they could have been in touch with each other. The 'science of men', as these biographical studies are referred to, led to the composition of bio-bibliographical compendia of scholars.
The methods of the Shiite legal tradition were inspired by Sunni developments in theology and law that took place in the vibrant intellectual climate of 9th-century Baghdad, some of which did not survive in Sunni Islam. One of these trends was speculative theology (kalam), practiced in its more rationalist form by the Mutazilites who often had Shiite leanings. While Mutazilism eventually died out, its principles and doctrines (such as free will or divine justice) had a great impact on Shiite theology and law. One of the methods of coming to a legal decision is that of making an independent effort (ijtihad) instead of simply endorsing an already existing view. In practice, Muslim legal scholars had to apply this principle whenever they were faced with a new situation. But while the 'door of ijtihad' was considered closed by Sunni scholars as early as the 11th century, the principle was endorsed by Shiites since the scholar the Allama al-Hilli.