Logic and the Sharia
Abu Hanifah (b. 700 - d. 767) was once accused of using logic to arrive at his fatwas ("a ruling on a point of Islamic law") which would eventually be incorporated into a school of law named after him, the Hanafi Madhhab.
In a conversation with the great Imam Muhammad al-Baqir, related by Muhammad Mojlum Khan in his The Muslim 100 - The Lives, Thoughts and Achievements of the Most Influential Muslims in History, Hanifah refuted the claim that reason played any part in his rulings, using as an example the revealed truth (an immutable fact revealed to a mortal by a god) about a male being entitled to a larger share of an inheritance.
4:11 Allah commands you, with respect to your children, that the male shall inherit the equivalent of the share of two females…
Hanifah: "Who is weaker, man or woman?"
Hanifah: "Which of them is entitled to larger share in inheritance?"
Baqir: "The Man."
Hanifah: "If I had been making deductions by analogy, I should have said that the woman should get the larger share, since on the face of it the weaker one is entitled to more consideration. But I have not said so."
The Hanafi Madhhab is considered by many the most "progressive" of the four mainstream Sunni schools of Islamic jurisprudence and the most widely followed; noteworthy countries include India, Pakistan, Bangladesh, Afghanistan, Turkey, Syria, Iraq and Egypt.
The century old upstart fundamentalist Salafi school or creed, which is closely associated with the Wahhabi doctrine promoted by the Saudis and is the Law of Islamic State, is the most dogmatic of the four mainstream madhhab.
Wahhabi theology sees the world in white and black categories—Muslim and non-Muslim, belief and unbelief, the realm of Islam and that of warfare. They [Wahhabi believers] regard all Muslims who [do] not agree with them as unbelievers to be subdued (that is, fought and killed) in the name of Islam.
John L. Esposito, Unholy War; Terror in the Name of Islam, Oxford University Press.