The Criteria for understanding the delineation of Islamic laws and principles are Quran and Sunnah.In my view this criterion must develop in parallel with advancement of human intellect in certain spheres.But the attitude of such delineation is of paramount importance. It, under no circumstance, should be that of a polemic or belittlement of the past scholars in any way. They have done their job in a tremendous way. Their dedication and commitment to understanding the true spirit of God's religion is beyond any doubt. Their respect and veneration must be depicted in our comments otherwise this entire effort is doomed to failure.
Having said that, their means and opinions must always be open to evaluation in the light of Quran and Sunnah to all people of all ages. They were never pertinacious on their thoughts and were always ready to revisit them. They all accepted the possibility that their views might turn out to be incorrect as the great exegete Imam Shafi once said,"I am convinced about the veracity of my opinions, but I do consider it likely that they may turn out to be incorrect. Likewise, I am convinced about the incorrectness of the views different from mine, but I do concede the possibility that they may turn out to be correct."