In introducing the chapter in the Torah dealing with moral chastity and sanctity of marriage, Moshe is told to speak to Bnei Israel and warn them: KEMA’ASEH ERETZ MITZRAYIM ASHER YESHAVTEM BAH LO TA’ASU, “You shall not follow the practices of the land of Egypt where you dwelt…”. (Lev. 18,3) Rashi points out that Egypt was the most morally corrupt land and Goshen where the Jews lived was the most corrupt part of Egypt. One may justly ask if this be true why the Jews were directed to live in Goshen.
Another fair question which can be asked is why Yaakov and his family continued to live in Egypt after the famine was over.
We read when Yaakov was on his way to Egypt Hashem appeared to him and told him not to fear to go there. He was promised to become a great nation there. Among a corrupt people the Jews, by living up to the ideals of the Torah, can become a guiding light for others. It is among morally corrupt people that Jews can have the greatest influence.
For centuries Jews lived in the Diaspora. This was not an accident but the design of Hashem. Their presence among the nations of the world had a positive bearing on all the people. Jews may have suffered by the hands of the nations, but their moral teachings did become part of the thinking of the world. That is why civilization is said to be a Judaic-Christian culture.