Origen on sinful nature and habit
"[...]Celsus seems to me to be quite wrong, since he does not allow the possibility of a complete change with people who have sinned by nature and who do this out of habit , and thinks that they are not even to be healed by punishment. It seems clear that all men have a natural tendency to sin, and that some not only have a natural tendency, but sin also by habit. But it is not true that all men are incapable of a complete change." (Con. Cel. III,66)