This is Seyyed Kamal's view on the importance to differentiate between what he calls tashayu' 'aqaedi (theological shiism), and tashayu' tareekhi (historic shiism):
When looking at all the different theological schools that exist today (school of Ahlul Bayt, Ash'ari, Mu'tazali, Zaidi, school of Ibn Taymiyah, etc), we must look at the sources they resort to to deduce their religious concepts, which are:
1) The Quran (the word of God), and
the valid hadith/narrations (words and deeds of the Infallibles)
2) The Intellect ('aql): not what we use as a tool to think and understa