“What is the difference between power and authority? Many exercises of power have no authority. And there are exercises of authority that do their work without power. Richard Nixon had the power of the presidency up to the moment he resigned. But after the disclosures of his role in Watergate he had no authority.
On the other hand, Abraham Lincoln never used, except in a few instances, the full power of the presidency; but had authority. He didn’t have to use sheer power. Pius XII, the pope who preceded John XXIII, hadn’t used the full power of the papacy. John XXIII never used the full outer power of the papacy, but he had enormous authority.
What is the difference? Authority is a force continuous with the whole nature and performance of the person or thing possessing it. My grandmother had authority; my grandfather had power. I remember what my grandmother said, and I wanted to do it. I have no remembrance of anything my grandfather said, except that I had to do it.
Scripture has both authority and power. It has great strength, but, most important, we want to do what it commands. That is its authority.”
– Joseph Sittler, Quotes from Gravity and Grace: Reflections and Provocations
This is a good question … and Sittler’s examples makes the discussion so much more on the ground and less abstract. Something to sleep on.