What is the Definition and Emergence of Usul Al-Fiqh?
The term usul al-fiqh is defined in the sources as follows:
Usul al-Fiqh is “The body of principles and investigative methodologies through which practical legal rules are developed from the foundational sources.”
Usul al-Fiqh is the science of methodology of Islamic jurisprudence which shows the independent jurist the methods and principles by means which he deducts the legal rulings such as recommended, prohibited, etc. from the detailed sources of law like the Holy Qur’an, Sunnah, consensus of Muslim jurists, and analogy. Usul al-Fiqh shows the foundations, principles, and sources of the science of fiqh.
The science of methodology of Islamic Jurisprudence was born at the end of second century of Hijrah.
During the time of the Messenger of Allah (pbuh), the rulings were established based on either the Holy Qur’an or the Sunnah of the Prophet (pbuh). After the Prophet (peace be upon him) passed away, the most prominent companions of the Prophet took on the task of issuing rulings and judgment regarding the problems of Muslim society. The Companions were people with unique ability of comprehension. They also lived together with the Prophet (pbuh) and were his friends for a long time. Because they practically applied the rulings of deducing rulings from the main sources of Islamic law, they did not need theoretical knowledge of such principles. They were very proficient in the Arabic language, which is the language of the Qur’an and Sunnah, and they knew the details and comprehended the purpose of every ruling. When they were in need of a ruling regarding a topic, they would turn to the Qur’an, and when they could not find what they were looking for in the Qur’an, they would turn to the Sunnah of the Prophet, and when they could not find any solution in them, they would issue their personal judgement, in other words apply ijtihad.
The independent jurists (mujtahids) of the generation that followed the Companions of the Prophet (or the generation of Tabi’un) followed the same way. After the eras of the generation of the Companions and that of Tabi’un had passed, new issues, which never had happened before, arose. Thus, mujtahids established the principles and methods to be used as the guidelines of issuing legal judgments in order to prevent the possibility of arbitrary judgments. The emergence of Usul al-Fiqh (the Methodology of Islamic Jurisprudence) as an independent branch of study took place towards the end of the second Hijri century. In this way, the books on the methodology of Islamic jurisprudence started to be compiled and the first one of such books was written by Imam Abu Yusuf, one of the prominent disciples of Imam Abu Hanifa. However, it did not survive to this day. The earlies books which have survived to this day is the book written by Imam Shafii titled “al-Risala”. This is because Imam Shafii is known as the father of the science of Methodology of Islamic Jurisprudence.
 Şaban, İslâm Hukuk İlminin Esasları (Usûlü’l-Fıkh), p. 28; Atar, Fıkıh Usûlü, p. 3.
Source: Hasan Serhat YETER, FIQH II, Erkam Pub.