I'm pretty convinced you have to believe in something. Even if it's just something like Mother Nature (with her evolution and earthquakes and shit - realizing how there are forces out of our control) and the power that other principles and events have on us that we can do nothing about. Religion is a widely accepted and practised way of holding yourself to a higher standard and to humility. But there are many ways to do that. The problem is a leftists tend to take this attitude towards politics which does not work. Or they are only interested in their version of morality - in other words they become selfish and arrogant.