Allah the Exalted said: {Then do they not contemplate the Quran, or are there locks upon [their] hearts?}1
So, by this statement, He urged contemplation and investigation through sound analogy (Qiyas), which is neither tainted by defect nor afflicted by absurdity. And in another place, He drew attention to the condemnation of blind imitation (Taqlid) and the abandonment of thinking.
So He, Glory be to Him, said:{And when it is said to them, "Follow what Allah has revealed," they say, "Rather, we will follow that upon which we found our fathers." Even if their fathers understood nothing, nor were they guided?}2
Thus, He indicated the obligation of scrutiny and inquiry regarding the Fundamentals (Usul), and submission to the Master of the Command (Sahib al-Amr) regarding the Branches (Furu').
I have found that every religious community has argued for and supported their religion with elegant proofs and explicit demonstrations, making them valid against the Divergent (al-Mubayin) and the Opponent (al-Mukhalif).