Some people believe that each Muslim has his/her own interpretation of Islam, and that all interpretations of Islam must be considered equally authoritative. Although it is true theoretically, since each human can believe in anything, and thoughts are difficult to control, let us have a closer look at it within the context of Islam.
In Islam one becomes a Muslim by declaring in presence of Muslim witnesses that there is no god but Allah and Muhammad is the Messenger of Allah. Koran, the direct words of Allah, makes only 14% of the Islamic Trilogy (Koran, Hadith and Sira). Thus Islam is 14% Allah and 86% Muhammad. God can be considered inexpressible and inconceivable. However anyone can understand the life story of a man.
In Islam it’s not enough to worship one God to be a Muslim. A Muslim is to worship Allah exactly the way Muhammad did it. So Muhammad is the highest authority in Islam. If someone claims he/she has a different, individual interpretation of Islam, equally authoritative, that would mean contradicting to Muhammad. Some Muslims reject Hadith in full or partially, claiming them to be made up after Muhammad’s death. But they don’t make even 1% of all Muslims for 2 reasons: first, by doing so they contradict to all Islamic scholars who have taught otherwise for 14 centuries. Secondly, Koran alone is not enough for practicing any of Islam’s Five Pillars. The details are contained in the Hadith.
So, if some individual Muslim believes he/she has a different interpretation of Islam, a personal way to pray, fast, give zakat, do hajj, different from what was prescribed by Muhammad, he/she has 3 options:
1) still do it the way the majority does, because the environment pressure is quite strong and not many people are able to withstand it
2) not do it, but keep silent, trying not to be noticed by others
3) speak out and proclaim having an individual interpretation different from Muhammad’s
The latter results in being accused of apostasy or blasphemy and such cases are dealt with in accordance with what prophet Muhammad prescribed doing. That is why Islam hasn’t changed much during the 14 centuries and is unable to be reformed into something tolerant and pluralistic.