Does he keep kosher out of respect for his father? Or observe Shabbat? The answer is no. But he still fasts on Yom Kippur. Not because he himself believes in God, but because his father did.
We might ask, Why does he respect his father? Because that’s what Jews do.
Why do Jews respect their parents? In the end it’s because that’s what the Ten Commandments say.
Why bother with the Ten Commandments? It can’t be because the man who fasts believes in God. He is adamant that he doesn’t.
But the bottom line is that since he still – despite not observing kashrut or Shabbat – lives by quite a lot of what God says in the commandments, we have to say ever so gently, “Sorry, my friend, but it seems that you do believe in God after all!”
Rav Kook, that great guide to Jewish spirituality, said that there really aren’t any Jewish atheists at all. No-one is completely without spiritual moments. No-one is devoid of religious feelings.
Maybe they don’t use the word God, but whatever they call it, they have a sense of the ultimate.
Rav Kook would say, “Sorry, my friend, but it seems you do believe in God after all!”
Rav Kook said something else that is very interesting. He said that the person who claims to deny God is to be commended for intellectual honesty. Such a person is clearly in search of truth, and they reject versions of purported truth that they find unsupportable. In the final analysis, theirs is a religious quest.
There is no-one who has rejected God, according to the Rav Kook line. They would like to believe in God; give them time, and the day will come when they will find truth and be able to call it God.