Chapter 64 【Case analysis】<The camera is mine>

The Public Security Bureau of a certain city caught a habitual thief and found a large amount of cash, cameras and other stolen goods in his residence.During the interrogation, the habitual offender was very dishonest and insisted that the cash was picked and the camera was bought from a thrift store a few years ago.The Public Security Bureau decided to interrogate the origin of the camera as a breakthrough, and the witness (the person whose camera was stolen) appeared in court to testify.The following is a transcript from the interrogation: Presiding judge: (asking the witness) Does the camera have any characteristics?

Witness: Yes, this camera is different. It has a hidden button. People who are not familiar with it can't find the hidden button, so they can't turn on the camera. Presiding Judge: Defendant, you turn on this camera. Defendant: Judge, if I open it, it will prove that the camera is mine!Yeah? Presiding judge: No, opening it does not prove that it must be yours; but failing to open it proves that it must not be yours. The defendant committed two sophistical errors.First, the witness said: People who are not familiar with the camera cannot open the camera. This judgment implies that whoever can open the camera is familiar with the camera, but the defendant secretly replaced it with whoever can open the camera. Second, from the point of view of reasoning, both the presiding judge and the defendant applied a hypothetical reasoning with a sufficient condition.

According to the rules of hypothetical inference with sufficient conditions, negating the latter can negate the antecedent, but affirming the latter cannot affirm the antecedent.For example, from the premise that if someone is from Shandong, he is Chinese, it can be deduced that if someone is not Chinese, he is not from Shandong, but it cannot be deduced that if someone is from China, he is from Shandong . The reasoning applied by the presiding judge was: if the camera is yours, you can turn it on; so, if you cannot turn it on, it proves that the camera is not yours. This is a correct hypothetical direct inference from negating the consequent to negating the antecedent (the inference with only one premise is called direct inference, and the inference with two or more premises is called indirect inference), also known as hypothetical commutation bit reasoning.

And the reasoning applied by the defendant is: If the camera is mine, I can open it; therefore, if I can open it, it proves that the camera is mine. This is a hypothetical direct reasoning from affirming the latter to affirming the antecedent, which violates the rules of inference and makes the mistake of affirming the latter.The presiding judge was keenly aware of this and pointed out: No, opening it does not prove that it must be yours. The defendant later failed to turn on the camera, forcing him to bow his head and plead guilty.This further confirmed the correctness of the presiding judge's reasoning and fully exposed the defendant's sophistry.