  The Mohists’ view of knowledge thus illustrates the practical orientation of early Chinese thought, as sketched in the discussion of fa (models) in the previous section. For the Mohists, knowing x does not require knowing the definition, the essence, the meaning, the Platonic Form, nor a description of x. It requires only the practical ability to distinguish x from not-x. This pragmatic view of knowledge contrasts with the semantic orientation of the Greek tradition, as epitomized by  Plato.[9]  We find Plato asking What is justice? and seeking to answer this question by determining the single essential form shared by all just things. By contrast, the Mohists never ask what the essence or definition of yi (righteousness) is. They are concerned only with the problem of how to reliably distinguish yi from not-yi. This problem can be solved, they assume, by finding appropriate models for drawing the distinction and teaching everyone to apply or emulate them. Such models may have a utilitarian, empirical basis; they may rest on independent moral grounds; or they may be based simply on the conviction that the actions of exemplary moral agents, such as Tian (Heaven) and the ancient sage-kings, cannot be wrong.