A person may escape from his country, his birthplace, his family home, and—consciously or by sheer distance—break with all that ties him to his homeland.
In the same way, a Jew may distance himself from his cultural heritage and even leave it entirely,sometimes also breaking off all social and family ties.
But a person cannot escape from his essential self.
In other words, a Jew may be assimilated, and even be the descendant of several generations of assimilated Jews, but he cannot—even if he is aware of it and wishes it—abandon the basic approaches inherent in him because of the very fact that he is a Jew.
These facets are indelible, even when this person is engaged in things that apparently have nothing to do with Jewish culture.
A person can observe anything in the world, either close or distant, but every subject he observes or deals with—whether it is close to the sphere of Jewish culture and affects it, or is detached from it and is even opposed to it—he can only see with Jewish eyes, and he can only think about it with the mind of a Jew.
–Rabbi Adin Steinsaltz
From We Jews, p. 158, by Rabbi Adin Steinsaltz