 It is in this matter that our common reason plays its critical role, which Xunzi understands in terms of our capacity to use the evidence of perception to make appropriate discriminations. For example, one sees two shapes, one triangular, the other square. Nothing in this differentiation of patterns forces one to attribute the name “triangular” to the first and “square” to the second. A single name could just as well be used for all three and four sided polygons. However, the senses have the effect of encouraging a distinct name for each; they are “evidence” (yuan, causes, means) for assimilating and differentiating objects in language. For instance, one may regard the assertion “Mountains and abysses are level” as inadmissible (or false), because it is contradicted by our perception of the non-level relation of the two geographical objects. This is the case, for Xunzi, even though it is convention, in the final analysis, that determines how the terms “mountain” and “abyss” are to be used. Xunzi’s point is not that the analysis of meanings somehow fixes how the terms of language are to be used, but that when convention does “fix ahead” (qi) the meanings of these terms, one is to use the senses to determine whether the objects to which they refer are to be treated as the same or different.