Existential fallacy

百度 9月24号什么星座

The existential fallacy, or existential instantiation, is a formal fallacy. In the existential fallacy, one presupposes that a class has members when one is not supposed to do so; i.e., when one should not assume existential import. Not to be confused with the 'Affirming the consequent', as in "If A, then B. B. Therefore A".

One example would be: "Every unicorn has a horn on its forehead". It does not imply that there are any unicorns at all in the world, and thus it cannot be assumed that, if the statement were true, somewhere there is a unicorn in the world (with a horn on its forehead). The statement, if assumed true, implies only that if there were any unicorns, each would definitely have a horn on its forehead.

Overview

An existential fallacy is committed in a medieval categorical syllogism because it has two universal premises and a particular conclusion with no assumption that at least one member of the class exists, an assumption which is not established by the premises.

In modern logic, the presupposition that a class has members is seen as unacceptable. In 1905, Bertrand Russell wrote an essay entitled "The Existential Import of Proposition", in which he called this Boolean approach "Peano's interpretation".

The fallacy does not occur in enthymemes, where hidden premises required to make the syllogism valid assume the existence of at least one member of the class.^{[citation needed]}

Examples

All trespassers will be prosecuted.
Therefore, some of those prosecuted will have trespassed.^[1]

This is a fallacy because the first statement does not require the existence of any actual trespassers (stating only what would happen if some do exist), and therefore does not prove the existence of any. Note that this is a fallacy whether or not anyone has trespassed.

References

^ "Logical Fallacy: The Existential Fallacy". www.fallacyfiles.org.

External links

[1] "Logical Fallacy: The Existential Fallacy". www.fallacyfiles.org.

[1]

2月14日是什么星座	新疆为什么天黑的晚	茉莉花有什么功效	月经量少吃什么调理最好方法	什么是唐氏综合征
疾厄宫是什么意思	儿童口腔疱疹吃什么药	血氨高是什么原因	县团级是什么级别	颈椎病用什么药膏
王字旁的字跟什么有关	青金石五行属什么	女性做B超挂什么科	易蒙停是什么药	彩虹什么颜色
小肠镜什么情况下需要做	一个三点水一个及念什么	乳酸杆菌大量是什么意思	angry是什么意思	柴火饭是什么意思

急性胰腺炎是什么病hcv8jop6ns6r.cn	苋菜是什么菜hcv9jop6ns2r.cn	尿酸高可以吃什么鱼hcv8jop1ns9r.cn	5.5号是什么星座hcv9jop0ns2r.cn	女人吃什么能活血化瘀bjcbxg.com
为什么会蛀牙hcv7jop6ns5r.cn	射手座是什么星座hcv9jop1ns2r.cn	风景旧曾谙是什么意思hcv8jop7ns0r.cn	女性绝经期在什么年龄是正常的hcv8jop9ns1r.cn	早上起床眼睛浮肿是什么原因hcv8jop0ns4r.cn
知了吃什么东西hcv8jop6ns8r.cn	三尖瓣反流什么意思hcv7jop4ns8r.cn	孕妇羊水少吃什么补的快hcv8jop5ns7r.cn	牙合是什么字hcv8jop2ns7r.cn	市公安局局长是什么级别hcv8jop2ns1r.cn
左上腹是什么器官hcv8jop7ns5r.cn	天麻炖什么治疗头痛效果最好hcv9jop0ns6r.cn	吃什么补肺养肺比较好hcv8jop9ns5r.cn	肚脐眼连接体内的什么器官hcv8jop1ns5r.cn	观音殿求什么hcv8jop5ns7r.cn

大华拼接屏/大华智能家居锁/大华监控工程/君卓科技

Overview

Examples

See also

References

External links