Islamic Legal Maxims

The oldest collection of Legal Maxims that has reached us is the Risalah 'usul, al-Karkhi (260AH-340AH)
By deep study of these 'usul it reveals that they are inclusive of qawa`id, dawabit, 'usul, and kulliyat. Some of them have the status of such general kulliyat that can be declared as the collective asset of Islamic Fiqh and some 'usul are such which may be useful in knowing the effective cause of Fiqhi values and to know the solution of Fiqhi problems according to the Hanafi way of proving a thing (istidlal) and the Hanafi style of logical deduction on a legal question (ijtihad) by a learned and enlightened doctor (Mujtahid).
Imam al-Karkhi is the author of the first existing book on legal maxims.
"...The style of Imam Karkhi is that he states the legal maxim in a small sentence while Imam Nasafi gives brief example. The principle and the example are so concise that a person who is not well-versed in Fiqh is not in a position to easily get the benefit of it. Here it should be remembered that the legal maxims of Imam Karkhi have undergone the process of refinement in the later centuries, and almost all the maxims at present are not in their original shape that was given to them by Imam Karkhi. For instance, out of the ninety-nine legal maxims given in Al-Majallah, only one maxim (article no. 4 of Al-Majallah) is partially stated according to the form of the first maxim of Al-'usul of Imam Karkhi. Otherwise, all the remaining maxims are present in Al-Majallah so far as their meanings are concerned, but the words and statements are not the same which were given to them by Imam Karkhi."[1]
Abul Hasan al Karkhi was a Hanafi Faqhi who wrote al Usul (d 340 H). He is among those who is known as al Mujtahidin Fil Masail; He was a contemporary of Imam ibn Majah, Abu Daud, Tirmidhi and Nasai.