Usul al-Fiqh is the knowledge of principles that show how Shariah rulings concerning people's actions are established from detailed proofs.
• Principles are disciplined rules for understanding.
• People's actions are the things people do, such as worship or a transaction.
• A detailed proof is the particular evidence connected to the ruling being studied. For example, a particular Quranic command about prayer is detailed evidence in a discussion of that command; merely saying “the Quran is a source” is a general statement.
The definition describes a method for understanding rulings. It does not mean that every learner derives a ruling independently.