核心畫面

One picture holds both uses: the part of a person that was never chosen, learned, or built — what you get simply by being a person. Nature here means the way a thing is before anyone shapes it, and human says whose. So human nature is the shared floor under everybody's behaviour. The first use points at that floor and describes it. The second use stands on it and says: of course they did that, we are all standing on the same floor.