One thing that Christianity did that other religions hadn’t done to quite that extent was introduce the concept of thought crimes. In the Gospels, Jesus tells his followers,
You have heard that it was said, ‘You shall not commit adultery’; but I say to you that everyone who looks at a woman with lust for her has already committed adultery with her in his heart.
In other places, Jesus is supposed to have said that it was not what someone did, but what someone thought that mattered – and that thought alone could “defile” a person. It’s not that the Old Testament didn’t contain references to “coveting” other people’s stuff, but Christianity made the sin almost entirely internal, not external. Without that focus on navel-gazing and internal thought policing, I’m not sure the ascetic movements in Christianity’s early history could have taken off, nor its emphasis on self-denial and mortification of the flesh.
All of this emphasis on subjective feelings comes at a price, however, and Christianity inflicts a particularly heavy and onerous burden on its followers by maintaining this idea. …