Some puzzling questions:
How come there are secular Jews, yet it would be meaningless to talk of secular Christians, secular Muslims, secular Buddhists... etc?
If you are secular, must you still rely on halacha to define 'Who is a Jew'?
If you light Friday night candles and make motzi, but don't believe it is a mitzvah (commandment), are you really practising Judaism?
No prizes if you know the answers.