The concept of "world religion" is historically based on a subjective perception of temporal or theological importance, usually from a Western, Christian or at least "Abrahamic" perspective. Early Christian scholars, the earliest known classifiers of major religions, recognized two "proper" religions, Christianity and Judaism, besides heretical deviations from Christianity, and idolatrous relapse or paganism. Islamic theology recognizes Christians and Jews as "People of the Book" besides idolaters. The Christian view long classified Islam as one heresy among others. Views evolved during the Enlightenment, however, and, by the 19th century, Western scholars considered the five "world religions" to be Judaism, Christianity, Islam, Hinduism, and Buddhism. These remain the classic "world religions."