According to British-Lebanese historian Albert Hourani, one of the reasons may be that "Islam had become more clearly defined, and the line between Muslims and non-Muslims more sharply drawn.
根據英國歷史學家阿爾伯特·胡拉尼（英语：Albert Hourani），其中一個原因可能是： 伊斯蘭教有更清晰的定義，穆斯林與非穆斯林是更明確的界線。