The verses 172 and 173 of the Surah Aaraf cer tify that...
They said: Yes, verily, We do testify : lest (so that) you should say on the Day of Judgment: " Verily, we have been unaware of this." (7:172) "or you can say: " our fathers before us have taken false gods, and we are their descendants after them. Will You destroy us on account of that which they followed" (7: 173) Muslim scholars quoting the Holy Prophet (as) and Imams(as) have described the scene of this covenant in different books. The full account of this story is as follows.
The event which Quran is referring in the above two verses, has occurred sometimes in the distant past i.e., before the bir th of man. Allah Subhanahu Taala gathered all human beings, who are from the lineage of Adam, in the form of minute particles and asked them to testify their faith in Him. All human beings in that state confirmed that they know the truth by saying : "We bear witness that You are our Lord". This testimony was then induced in every soul.
Any soul which takes birth whether in a Muslim or a non- Muslim family comes with this inborn knowledge which is enough for him to achieve the truth and reject the falsehood.So, all human beings, whether born in a Muslim or nom-Muslim family, are equally equipped to achieve the truth and are therefore equally responsible for what they believe irrespective of their personal background.
On Islamic standard, a person is not qualified to be called as Muslim just because he is bor n in a Muslim family. It is only for the sake of convenience in social dealings that Islam recognizes every born Muslim as Muslims. But the basic criteria of being a Muslim is the same for everyone whether he is a born Muslim or born non-Muslim.
The basic criterion for any person to be called as a Muslim is that he has intellectually recognized the basic concepts of Islam and he consciously observes the Islamic laws . This means that a Muslim is one whose faith is based on his research and deep understanding of Islam. He has not inherited his faith from his father but he has realized the truth and has accepted it because of its merits.