Hard, White and the Discourse That Divided a Single Stone Into Two Objects

Gongsun Long's other surviving argument is less famous than the white horse but structurally similar, and turns on a single hard white stone. Touch the stone and you perceive its hardness but not its color; look at it and you perceive its whiteness but not its hardness, since no sense organ delivers both properties at once. From this Gongsun Long argued that hardness and whiteness, though both real properties of the one stone, are never actually given together in any single act of perception, and pressed the question of what it even means to say a hard white stone is a single, unified object rather than two properties merely co reported by two different senses about the same location.

Contemporaries and later readers split over whether this was a serious metaphysical claim about how properties relate to the objects that bear them or a display of clever argument for its own sake, the same charge of sophistry leveled against the white horse argument, and the later Mohist Canons took the dispute seriously enough to answer it directly, arguing that hardness and whiteness do occupy one and the same stone whether or not any single perception ever registers both together, treating the question as one about the structure of reality rather than the limits of a given sense. The disagreement is one of the clearest surviving instances of one Warring States school reading another's argument closely enough to construct a formal rebuttal, evidence that the disputers' reputation for argument for its own sake did not stop rival schools from taking their conclusions as claims that needed answering.