translation.en: Rocks feel hard and impenetrable to our hands, precisely because objects like rocks and hands cannot penetrate each other. It's therefore useful for our brains to construct notions like "solidity" and "impenetrability," because such notions help us to navigate our bodies through the middle-sized world in which we have to navigate.
translation.zh: 岩石在我们的手中感觉是坚硬且不可穿透的 是因为岩石和手这类物体 并不能互相穿透。因此，这对于我们的大脑而言， 将此类概念定义为“固体”和“不可穿透”是有用的。 因为此类概念可以帮助我们在这种中等尺寸的世界中 操纵我们的身体，并且我们不得不这样做。