The word ‘Jewish’ is open to more than one interpretation.
I remember once staying at the Scots Hotel, Tiberias, Israel (great restaurant, by the way). One of the features they offer visitors is a lecture about the hotel, its history and guidelines. They emphasize the fact that one third of the employees are “Christians”, another third are “Muslim” and another is “Jewish”. The obvious conclusion: ‘Jewish’ is a religion, and there are no secular employees in that hotel.
As defined by the Nuremberg laws in 1935, a “Jew” was a person – regardless of religious affiliation or self-identification – who had at least three grandparents who had been enrolled with a Jewish congregation. The modern State of Israel accepts Jewish immigrants largely based on a similar law. The obvious conclusion: ‘Jewish’, if you will, is a congregation, an ethnic group of people.
Things are simpler in locations like Belgium, for instance. Mathematically speaking, all citizens have an attribute called ‘nationality’. The value for this attribute is ‘Belgian’ for all of them. They have another attribute that describes their ‘congregation’ or ‘culture’ or ‘ethnicity’, which (putting the Jews aside for a moment) may hold the values ‘Flemish’ or ‘Walloon’, and recently also commonly ‘Arab’. As far as the ‘religion’ attribute is concerned (again, ignoring the Jews for a second), it may hold values such as ‘Christian’ or ‘Secular’ or ‘Muslim’. So you can have valid combination like ‘Christian Flemish’ or ‘Secular Walloon’.
Thus, there may be ‘Muslim Arabs’ and there may be ‘Christian Arabs’, and of course ‘Secular Arabs’, God bless them. But are there ‘Jewish Jewish’ as opposed to ‘Secular Jewish’? Or even, are there ‘Muslim Jewish’ people? According to Nuremberg there certainly can be.