Good question.Everything in Islam is based on the solid sources of the Quran and the Sunnah. But, just as the scholars must revert to Ijma’ when a clearly stated solution isn't readily known from the Quran and Sunnah text, just the same, when a Muslim individual finds himself in a situation where he has exhausted all that is available from Quran, Sunnah, and Ijma, then he reverts to ‘Aql using the aforementioned 3 sources as his foundation.
