Legal theory, the discipline of the study of the roots or sources of law, and of how to interpret them to arrive at legal rulings.
The sources of law are traditionally listed as four:
Of these, only the first two are revealed sources; the others are devices governing their interpretation.
Other sources that are acknowledged by different schools include:
The interpretation that a jurist performs in deriving an answer to a new legal question from the sources of law is called ijtihad (diligent inquiry).
The goal of usul al-fiqh is to determine which of the five legal values should be assigned to every human act. (The knowledge arrived at is called fiqh, the branches of law).
This requires analyzing the language of the Qur'an and Sunna to determine their meaning and resolve apparent contradictions, using concepts such as:
Other mechanisms provide answers to legal problems without reference to the meaning of the sources:
In the traditionalist view, only an expert (a mufti, or issuer of legal opinions) is qualified to arrive at legal judgments, and others must follow his opinions, which may be right or wrong, but are always sufficient for gaining God's reward and avoiding punishment.