The balance between revelation and reason has fundamental importance in IslamicTheology which is most likely we can trace it to the early times. A constructive reasontogether with revelation has been the radical need of Muslim Theology; however somedeviations and assaults in its history prevented it from functioning its task. A closeexamination of ?reason? in the Qur?an will show us how functionel it is indeducing/inferring some basic principles in our intellectual and practical life.