In the story, it is the Samaritan who is free. He is sovereign, in that he is acting according to his own values and is able to realize them in the world. The road that he walked was material, but not only. We are in nature but not entirely of it. Our bodies are subject to inertia, but we can choose to stop by the side of the road. Our bodies are pulled down by gravity, but we can raise someone else up from the ditch.
We are in nature but not necessadily of it...true freedom to act differently.
