(Surah al-Maaida...
(Surah al-Maaida, 5:104) This strong condemnation of the idol-worshippers for following their fore-fathers blindly has been repeated elsewhere: And when it is said to them, "Follow what Allah has sent down," they say, "No, but we will "follow such things as we found our fathers doing." (Surah al-Baqara, 2:170; Surah Luqman, 31:20) Islam says that one may consider the views and opinions of others, but that one should only accept that which is reasonable to believe: “So (O Muhammad) give good tidings to My servants who give ear to the word and follow the fairest of it.
Those are the ones whom Allah has guided, and those are men possessed of minds." (Surah az-Zumar, 39:17) Likewise, in the books of ahadith we find the Prophet and the Imams of Ahlul-Bayt using intellectual arguments in matters of belief to convince their opponents or the seekers of truth. This itself is an example and sunnah for the Muslims to base their belief on understanding and conviction. But as for the "branches" of religion, Islam expects absolute obedience from the Muslims.
The reason for this expectation is very obvious: Once a person has believed, by his own free-will, in Allah as the Creator and the Wise Author of laws, in Muhammad as the infallible Messenger of Allah, and in the Qur'an as the authentic message of Allah-then it follows as a necessary consequence that he must adhere to the shari' ah laws.
This absolute obedience about the shari'ah laws can be inferred from the following verses: “It behooves not a believing man and a believing woman that they should have any choice in their affairs when Allah and His Messenger have decided a matter; and whosoever disobeys Allah and His Messenger, he surely has strayed off a manifest straying.” (Surah al-Ahzaab, 33:36) “O you who believe!
Do not take precedence before Allah and His Messenger (in shari'ah matters), and fear Allah; surely Allah is Hearing, Knowing.” (Surah al-Hujuraat, 49:1) “O you who believe!
Obey Allah, obey the Messenger and those who are in authority among you (i.e., the Imams).” (Surah an-Nisaa’, 4:59) “We have not sent a Messenger but to be obeyed.” (Surah an-Nisaa’, 4:64) To summarize: In Islamic beliefs, a Muslim is expected to believe only after reflection; and in Islamic laws, he is expected to follow them without any reservations. The Categories of Shari' ah Laws Now we come to the problem that why such and such law of the shari'ah was legislated.