'Principle' in the Bible

What, then, is there to boast about? That has been eliminated. On what principle? On that of actions? No, but on the principle of faith.

So I find this to be a principle: when I want to do what is good, evil is right there with me.

but I see in my body a different principle waging war with the Law in my mind and making me a prisoner of the law of sin that exists in my body.

Now may peace be on all those who live by this principle, and may mercy be on the Israel of God.