Chanes suggests that these six stages could be merged into three categories: "ancient antisemitism, which was primarily ethnic in nature; Christian antisemitism, which was religious; and the racial antisemitism of the 19th and 20th centuries". In practice, it is difficult to differentiate antisemitism from the general ill-treatment of nations by other nations before the Roman period, but since the adoption of Christianity in Europe, antisemitism has undoubtedly been present. The Islamic world has also historically seen the Jews as outsiders. The coming of the Scientific and Industrial Revolutions in 19th-century Europe bred a new manifestation of antisemitism, based as much upon race as upon religion, which culminated in the Holocaust that occurred during World War II. The formation of the state of Israel in 1948 caused new antisemitic tensions in the Middle East.