Hello, I’m Matthew Harris.
大家好 我是Matthew Harris
I’m a philosophy graduate student at Duke University,
我是杜克大学的一名哲学毕业生
and today I’ll be discussing
今天我将讨论一下
the formal fallacy of denying the antecedent.
形式谬误中的“否定前项”
‘Denying the antecedent‘ is a formal fallacy,
“否定前项”是形式谬误中的一种
meaning that the argument has a flaw
其意思是指一段论证中
contained in its logical form.
存在着一种逻辑形式上的缺陷
This is important because
这一点很重要 因为
whenever this pattern of argument occurs,
一段论证无论其有着何种主题或内容
regardless of topic or content,
一旦出现这种论证方式
the argument will always be invalid.
那么此论证就会是无效论证
So how can we tell when
那么我们该如何判断
the fallacy of ‘denying the antecedent‘ occurs?
这种“否定前项”谬误的出现呢？
Well, it happens when we mistake
其实呢 这种谬误会发生在当我们混淆
the direction of a conditional,
单一条件的方向
or confuse it for a biconditional.
或者是将其混淆为双向条件之时
And it starts with the denial of
并且这种谬误一开始会否认
the conditional statement’s antecedent,
条件句中的先决前提
then concludes the denial of its consequent.
然后得出一个否定其结果的结论
The logical form of arguments that commit
犯了“否定前项”这种谬误的论证
the fallacy of denying the antecedent look like this:
其逻辑形式看起来是这样的：
‘If P, then Q. ’
“如果P 那么Q”
‘Not P. Therefore, not Q. ’
“若非P 即非Q”
Now, let’s take a look at this conditional:
现在 让我们一起来看看这个条件例句：
‘If you are a ski instructor,
“如果你是一个滑雪教练
then you have a job. ’
那么表示你有着一份工作”
The antecedent statement of this conditional is
这个句子的前提是
‘you are a ski instructor, ’
“如果你是一个滑雪教练”
and the consequent is ‘you have a job. ’
结果是：“你有一份工作”
But suppose someone made an argument
但是假设有人做出的论证
with this conditional as its first premis:
是以这段论证的条件为前提：
Premise (1): If you are a ski instructor, then you have a job.
前提一：如果你是一个滑雪教练 那么表明你有一份工作
Premise (2): But you are not a ski instructor.
前提二：但你并非是一个滑雪教练
Conclusion: Therefore, you do not have a job.
结论：因此 你没有工作
Here, the second premise is a ‘denial of the antecedent‘.
留意此处 第二个前提即“否定前项”
This premise does not tell us
此前提并未告诉我们
that only ski instructors have jobs.
只有滑雪教练才有工作
So, even if the conditional statement is true
因此 即使此条件例句的陈述为真
that ski instructors have jobs,
即 滑雪教练有工作
it cannot be inferred that
其并不能推断出
‘if you are not a ski instructor, ’
“若你并非是滑雪教练
‘then you are unemployed. ’
那么你就处于失业中”
A conditional could validly
还有一种条件句会有效地
be used to argue for the truth of this consequent
通过肯定前项的方式
by affirming the antecedent.
推断出一个结果为真的论证
We find this in the arguments
我们发现在这种论证中
of a form called ‘modus ponens. ’
含有一种叫作“假言推理”的论证形式
It is also valid to argue from the denial of a consequent
但这种形式依旧是通过从否定后项来否定前项
to a denial of the antecedent.
以进行有效论证的
But it is never, ever valid to deny the antecedent
但是 一个论证若通过否定前项来否定后项
to reject its consequent.
是永远不会成为一个有效论证的
Let’s try another example:
我们来试试另外一个例句：
‘If you are a property owner, then you are a human. ’
“如果你是一个有产者 那么表明你是人类”
‘But you are not a property owner, ’
“可你并非一个有产者”
‘Therefore, you are not a human. ’
“所以你就并非是人”
The antecedent, that you are
这个例句中的前项是：
a property owner, is being denied.
“你是一个有产者”被否定了
Even though you need to be a human to own property,
即使你需要成为人才能拥有产权
this has no bearing on humans who do not own property at all.
这和那些没有产权的人无关
For example, graduate students.
比方说 一个刚刚毕业的学生
Let’s consider one last example:
让我们再去思考最后一个例子：
‘If anyone is watching this video, ’
“若有人在观看这个视频”
‘then they are on the internet. ’
“那么表明他们在上网”
‘Some people are not watching this video, ’
“而那些没有在看这个视频的人”
‘Therefore, they are not on the internet. ’
“则他们都没有在上网”
Again, ‘denying the antecedent’
这个例句又一次犯了“否定前项”的错误
by pointing out that not everyone
其通过指出“并非所有人
is currently watching this video
都在观看这个视频“的这一前项
does not validly demonstrate the denial of the consequent,
做出了一个“否定后项“的无效论证
that they’re not on the internet at all.
即 (那些没有看这个视频的) 人们都没有在上网
These have been a few cases
这些都只是少数情况
that I hope will come in handy
但是我希望能够对你们有所帮助
in avoiding this formal fallacy in your own arguments.
以防这种形式谬误会出现在你们的论证中
For more related to the fallacy of ‘denying the antecedent’,
如果你们想知道更多关于“否定前项“的逻辑谬误
I recommend that you take a look at the other related videos
我推荐你们再去看看其他的关于这方面的视频
on informal and formal fallacies,
例如形式谬误和非形式谬误
the fallacy of ‘affirming the consequent‘, and conditionals.
以及“肯定后项“或者其他的条件谬误
Subtitles by the Amara.org community.
本视频字幕由Amara.org community提供