It's the one that stands in the open where it is compelled to struggle for its existence against the winds and rains and the scorching sun. So we must act as the bird and block out our fears. Then we will be able to soar higher than we ever imagined. It is a privilege denied to many. Service is a principle.
Love is a principle.
Hard work is a principle. Respect, gratitude, moderation, fairness, integrity, loyalty, and responsibility are principles. There are dozens and dozens more. They are not hard to identify. Just as a compass always points to true north, your heart will recognize true principles.