Thus, if Christians hold such a view of religions, one of them leaving his religion becomes like a person moving from one school to another. People frequently do this out of desire or fear. If his relatives and friends remain in the first school, he does not object; rather, he continues inwardly to love and cherish them. For a school is like a homeland, and the soul longs for its homeland unless it believes that remaining there is forbidden or entails harm and worldly loss.
For this reason, many among the People of the Book who outwardly profess Islam make no distinction between Muslims and the People of the Book. Some incline more towards Muslims, while others incline more towards their former religion. Others are drawn to their former community by temperament and habit, or by ties of ethnicity, kinship, homeland, cooperation in pursuing their aims, and the like.
Likewise, the philosophers and those who follow their path, such as the Qarmatians, the Ittihādiyya, and others like them, consider it permissible for a person to follow the religion of the Muslims, the Jews, or the Christians. It is well known that all of this constitutes disbelief by the consensus of Muslims. Whoever does not acknowledge, inwardly and outwardly, that Allah accepts no religion other than Islam is not a Muslim.