Logic, linguistics, and philosophy. Culture and politics
Jewish identity
If a Christian rejects Christianity, then he’s no longer Christian. But it’s different for the Jews. Some Jews go so far as to hate Judaism, but that doesn’t make them any less Jewish. A born Jew is inescapably Jewish. Consider Sigmund Freud: He had little respect for Judaism, but he had a lot of pride as a Jew, which led him to Zionism. He was part of the trend that started in the 19th century of making Jewish identity less about being a believing, practicing Jew, which is how Jews have traditionally identified with each other, and more about identifying with each other like any other national group.
There are strong biological patterns in the Jews. For example, the Ashkenazi Jews were so endogamous for so long that they’ve become biologically distinct. The Ashkenazi bloodline is unique. But it’s not the biology that makes the Jew. It’s possible for two people to have the same amount of Ashkenazi blood but for one of them to be Jewish and the other not.
The Jews are neither strictly an ethnoreligious group (for having a Jewish identity doesn’t necessarily mean being religious or making Judaism part of your identity) nor strictly an ethnonationalist group (for having a Jewish identity doesn’t necessarily mean being nationalist or making Israel part of your identity). There’s also nothing biological or racial that distinguishes every Jew from every non-Jew. There are “white” Jews, “black” Jews, etc. There are Ashkenazi Jews (with some European blood of one kind), Sephardic Jews (with some European blood of another kind), etc. Most Jews descend in part from the Ancient Israelites, but there are some exceptions: the converts with no Jewish ancestors. Etc etc. So what kind of group are the Jews? They’re a quasi-ethnoreligious, quasi-ethnonationalist group with strong biological/racial patterns. There are (1) believing, practicing Jews, (2) Zionist Jews, (3) believing, practicing Zionist Jews, and (4) Jews who want nothing to do with Judaism, Zionism, or anything else Jewish. There are the Jews who were born into the Jewish extended family, and there are the Jews who were “adopted” into the Jewish extended family: the converts. Etc.