There is no difference of opinion amongst Muslim sects that the ‘religion’ of Allah is Islam; that the only way to know Islam is through the Book of Allah and the sunnah of the Holy Prophet; and that the Book of Allah is what is known as the Qur’an, is without any addition or subtraction.
And what difference is there is in the interpretation of some of the verses of the Qur’an; and in believing or not believing some of the sunnah as genuine; or in its interpretation.
This difference of approach has led towards the difference in some basic principles and some laws of shari’ah.
As the basic principles of Islam are well-known, I do not think it necessary to enumerate all the beliefs. It will be sufficient if some of the important differences are described here to give the readers a fairly comprehensive idea of the main characteristics which distinguish the Shi’ahs from the Sunnis.
All the Muslims agree that Allah is one, Muhammad is His last Prophet and that one day Allah will resurrect all the human beings and all will be answerable to their beliefs and actions.
All of them agree that anyone not believing in any of the above three basic principles is not a Muslim. Also, they agree that anybody denying the famous tenets of Islam, like salah (prayers), sawm (fasting), hajj (pilgrimage to Mecca), zakat (religious tax), etc., or believing that the famous sins, like drinking wine, adultery, stealing, gambling, lie, murder, etc., are not sins, is not a Muslim, though he might have been believing in Allah and His Prophet Muhammad, because to deny such things is tantamount to deny the Prophethood of Muhammad and his shari’ah (Divine Law).
When we go further, we come across those subjects which are not agreed amongst the Muslims, and there the differences between the different sects of Islam begin.