Chapter 65 <Killing is not killing>

The Mohist school in the Spring and Autumn and Warring States periods of our country made important contributions to the study of formal logic, but there were also mistakes in Mohist logic.For example, in Mohist's "Xiao Qu", there is such a reasoning: robbers are people; killing robbers is not killing people. From the premise that robbers are human beings, can we draw the conclusion that killing robbers is not murder?cannot.Because in the premise, the robber is included in the extension of man, but in the conclusion it is excluded from the extension of man, which not only changes the extension of the concept of man, but also changes its connotation. It makes the concept of man lose its own certainty and coherence, and violates the law of identity and non-contradiction, thus constituting sophistry.

In addition, judging from some examples of reasoning in "Xiaoqu", it cannot be justified.For example, there is such a reasoning in "Xiao Qu": a white horse is a horse; riding a white horse is riding a horse.We think this reasoning is correct, it is the negation of the reasoning of killing robbers and not killing people. Some comrades in the field of logic in our country defend the reasoning that killing robbers is not murder. They say that killing robbers is not killing people, referring to ordinary people other than robbers.This explanation is obviously untenable, because it is contradictory to the premise that robbers are humans, and the two cannot coexist.Some comrades want to use the reason that killing an enemy is not a crime of homicide to prove that killing robbers is not murder.This reason is also untenable, because the crime of not committing homicide and not murder are two completely different concepts, and the former cannot be used to replace the latter.

For example, can we prove that killing a pig is not a pig on the grounds that it is not a crime to kill a pig?It can be seen that defending sophistry will inevitably fall into sophistry.