I have to ask this because this is where my understanding breaks down, and if I'm honest, it is something that has perplexed me my entire adult life. How can one be a secular (non believing) Jew? Surely you either believe in the central tennets of the Jewish faith, or you don't, in which case you aren't Jewish. I was raised a Catholic, but I realised shortly before I was confirmed that I didn't believe in any of it (I was still confirmed, the school didn't give you a choice). If the question is asked, I don't describe myself a non-beliving Catholic, I call myself an atheist.
Just because! That's the $64,000 question, Mark, and there's no simple answer but I'll try.
Judaism is a religion but it's also a culture and a people. It's not a race because I can take you around London and introduce you to Jews who are black Africans and others who are blue-eyed blondes but perhaps calling us a race is the nearest understandable explanation. Not all Jews look like Golders Green "Yeshiva Bochers" ["Talmudic scholar boys"] who dress like something out of 18th century Poland.
The last time I discussed this, was with a Jewish guy who was selling to my business and we ended up agreeing that no one could really define Judaism. "It's a thing" we agreed. It's different. "It just is!". But he told me a lovely story.
He was on holiday in China. I can't remember which city, but it wasn't Beijing or a major tourist attraction, when he heard a call over the hotel tannoy saying, "If there are any Jewish gentlemen in the hotel, could they come to reception!?" So he did. It turned out that an old Jewish man had died somewhere in the city and they were trying to gather a "minyan", a group of ten adult Jewish males to say Kaddish [the prayer for the dead] over his body. And in that city in the middle of China they found ten Jews!
Perhaps part of Jewish identity comes from a history of persecution and anti-semitism. As I said earlier, in living memory it didn't matter whether German and European Jews were religious or atheist, totally integrated or married into Catholic families. Whether they observed religious festivals or ignored them. Almost uniquely in history, Jews are a group who have found themselves defined by others.
For information, the shooting in Copenhagen late last night, was an attack on the reception after a Bat Mtzvah - for a 13 year old girl and her family. And the unarmed guy who was murdered, died protecting the 80 family and friends who were celebrating inside and who would all have been targets if the gunman had gained entry.