What are the controls for the application of reason in creed, and how is faith in creed achieved without doubt?

Islam is a religion of natural disposition (fitra) and intellect, based on revelation, and it does not contradict sound reason. The role of intellect in religion is to ponder over the texts and reflect upon revelation, not to control it. A distinction must be made between someone born Muslim and someone born non-Muslim. The former may experience doubt or misgivings, the cure for which is found in the Qur’an and Sunnah. The latter is invited to Islam through methods derived from revelation. As for Cartesian philosophy, which is based on doubt, it is blameworthy and leads to the denial of truths. A sound intellect does not deny what is known by sense and necessity, and the Sharia does not contradict sound reason that is free from suspicions and desires.