What are Silas' motivations, based on his actions in the first couple of chapters?

Silas seems deeply religious, believing that his violent acts of war are the will of God. He also practices corporal mortification, which is supposed to remind him of the sacrifice of Christ by wearing a belt lined with barbs on his thigh and beating his own back with a rope until blood is drawn. This indicates that, though his actions are violent, he feels that they are justified by his religious beliefs.