What are the reasons that have led to the emergence of multiple Islamic ideological schools? What is the effect of this on the Muslim individual and community?
What are the reasons behind the occurrence of multiple Quranic commentaries? What is the effect of this on the Muslim individual and community?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu 'alyhi wa sallam, is His slave and Messenger.

When observing Islamic groups, you will realize that all of them are established on ideas that aim to apply the rules of the Sharee'ah. However, the founders of these groups differ on priorities in terms of different aspects of Islam.

Some groups are of the view that it is necessary to start with reforming the heart. They believe that a righteous heart makes a  righteous man and a corrupt heart makes a corrupt man, and thus a righteous or corrupt community.

Others maintain that it is necessary to focus on establishing an  Islamic state which rules according to the Sharee'ah. They believe that achieving this target should lead to the uprightness of the entire nation. To support their view, they quote the following verse: Allaah The Almighty Says (what means): {[And they are] those who, if We give them authority in the land, establish prayer and give Zakah [obligatory alms] and enjoin what is good and forbid what is evil. And to Allaah belongs the outcome of [all] matters.} [Quran 22: 41]

A third group aims to refine Muslim creed from the filth of Shirk (polytheism). They focus on establishing a valid creed in the hearts of believers and eradicating all aspects of Shirk, because it is an unforgivable sin.

These three ideologies complement each other, because they cover the fundamental issues of Islam. Their differences are  about priorities only, away from the essence of Islam.

As for the reasons behind the occurrence of multiple Quranic commentaries, it is because the Book of Allaah, the Quran, is so rich in knowledge that it is impossible for scholars to cover and fully explain all of it. Therefore, each has set out to extract information within the limits of his capacity. Some scholars focus on interpreting verses of the Quran in light of the Quran, the Sunnah and comments of the righteous predecessors' scholars. This methodology was adopted by the Shaafi‘i scholars At-Tabari and Ibn Katheer and others.

Other scholars of Tafseer (exegesis) focus on extracting rulings of the Sharee’ah from the Book of Allaah. This methodology was adopted by, for example, the Maaliki scholars Al-Qurtubi, Ibn Al-‘Arabi, Ash-Shinqeeti and others.

Other scholars adopt a linguistic approach in their commentary. This approach was adopted by Az-Zamakhshari and Abu Hayyaan .

It is noticeable that the various efforts of scholars in this regard complement each other, each giving Muslims a precious reference for the exegesis of the Book of Allaah The Exalted and serving the benefit of the Islamic nation.

However, being mortal human efforts, they may have certain defects. Therefore, we must praise them when they are right and overlook their faults, which are relatively little in comparison to their good deeds.

Allaah Knows best.