'Aql

'intellect') is an Arabic term used in Islamic philosophy and theology for the intellect or the rational faculty of the soul that connects humans to God.

[7] In the perspective of Islam it is precisely ‘aql which keeps man on the straight path (the sirat al-mustaqim) and prevents him from going astray.

The answer, according to the Quran, is that only the ūlu’l-albāb (the possessors of intellects) are the ones who remember and understand the significance of God's signs.

The connection between intellect and sound religious faith and practice is emphasized in both Sunni and Shia traditions.

In that vein, Imam Jaʿfar al-Ṣādeq defines intellect as the means by which one worships the All-Merciful and attains Paradise.

[8] The term ‘aql was heavily elucidated by early Shī‘ah thinkers; it came to replace and expand the pre-Islamic concept of ḥilm (Arabic: حلم) "serene justice and self-control, dignity" in opposition to the negative notions of ignorance (jahl) and stupidity (safah).

Among Twelvers, Akhbārīs (associated with exotericism and traditionalism and theological schools in Qom) and Usulis (associated with esotericism and rationalism and theological schools in Baghdad) were contending subschools: the former reject ijtihād outright; the latter advocate ijtihad and have been predominant for the last 300 years.