One of the most important questions is that of the relationship between ‘aql (reason-intellect) and the revealed law (shar’iah) – There are at least three positions regarding this issue.
1- The first position is that of Mu’tazilites who said:
العقلُ میزان الشریعة
‘Reason is the criterion of the divine law’
They accepted only those religious principles and rulings that were consistent with reason. They rejected those aspects of the shari’ah the secret of which their reasons could not comprehend.
2- The second position is that of the mutikallimun who held:
العقلُ مفتاح الشریعة
‘Reason is the key to the divine law’
They taught that reason is helpful only insofar as it leads us to the treasury of religion. Once we have access to the treasure, we do not need the key anymore.
Hence, the mutakallimun used reason only to demonstrate the coherence of their beliefs. Some of them even rejected any rational/intellectual principle that went against the letter of the law.
3- Mulla Sadra (r.a) opposes these two opinions firmly and holds a third position which is more accurate. For Mulla Sadra (r.a),
العقلُ مصباح الشریعة
‘Aql (reason-intellect) is the lamp of the shari’ah’
‘Aql is the lighted lamp and the divine law is the path. If one does not walk on the path, the lamp is of no use. If one does not possess a lamp, one cannot see the way. Without ‘aql, what remains of religion is the outer shell. This shell cannot provide us with any certainty in religious issues.
Mulla Sadra (r.a) writes: ‘Those who consider the philosophers to be people of bid’ah (innovation) are people of ghaflah (ignorance); it is not a bid’ah to think, but it is bidáh not to think. This lack of ta’aqqul (reasoning/intellection) is worse than any innovation in our religion.