 How do we determine whether something is “this” or not? As explained in  section 4.1,  we cite a  model or paradigm (fǎ 法)  of the kind in question and try to show that the thing is or is not relevantly similar to it. A thing is “so” (rán 然) when its “looks” (mào 貌, observable features) are similar (ruò 若) to the model (fǎ) (A70–71). Models may include a thought of the thing, measuring tools or other devices for identifying it, or concrete examples. Things can “match” (hé 合) the model “exactly,” as when a circle is exactly the same shape as the model, or by what is “appropriate,” as when we deem a man “swarthy” by the color of his skin, not his hair or eyes (A83, A96). The overall process of citing a model, explaining the reasons for distinguishing something as “this” or “not-this,” and thus achieving understanding is called “explanation” or “persuasion” (shuō 說) (A72, NO11). “Explanation” (shuō) is the analogue, in the Chinese context, of giving an argument for a claim. However, an “explanation” has no particular formal structure. Nor is it regarded as proving a conclusion; the Mohists develop no conception of deductive proof. It is simply the process of explaining the grounds (gù 故) for distinguishing something as “this” or “not-this.” 