Where the text is silent, someone still has to answer the question.
Every legal tradition eventually meets a case its founding texts never anticipated. A society can respond to that gap two ways: reason a new answer out of the tradition’s own principles, or default to silence and say nothing further can be decided. Classical Islamic law built a formal mechanism for the first option and gave it a name: ijtihad.
The word comes from the Arabic root j-h-d, exertion of effort, the same root behind jihad. Technically, ijtihad is the sustained, disciplined effort of a qualified jurist, a mujtahid, to derive a ruling on a question the Qur’an, the Sunnah, and prior scholarly consensus (ijma) do not directly settle, typically through analogical reasoning (qiyas) or independent judgment (ra’y) grounded in those same sources. It is not free-floating opinion. Classical jurists set a demanding bar for who could exercise it: command of Arabic, deep knowledge of the Qur’an and hadith sciences, awareness of prior consensus, and sound legal judgment. A jurist who met the full standard was called a mujtahid mutlaq, an absolute mujtahid, entitled to reason from the sources directly rather than within the confines of an established school.
Ijtihad’s structural opposite is taqlid, deference to an already-settled ruling rather than re-deriving it. Historians dispute how completely ijtihad receded after the classical period, but the concept itself never left Islamic legal theory, it remained the named alternative to imitation, invoked by every reformist who argued the tradition needed to think again rather than simply repeat itself. Muhammad Iqbal made the most influential twentieth-century case for that revival, recasting ijtihad as what he called the principle of movement in Islam, the built-in mechanism by which a permanent framework of values stays capable of addressing a changing world.
Source: Encyclopaedia Britannica, “Ijtihad”; Wael B. Hallaq, “Was the Gate of Ijtihad Closed?” International Journal of Middle East Studies 16, no. 1 (1984).