《超越感觉》第七章：什么是论证？（85-87页）翻译

评估论证

最基础的评估论证的方法陈述如下：确定前提正确与否，从前提到结论的推理是否有效。如果符合两个标准，那论证就是完整的。当论证是清晰的，完整的陈述出来，而且你正确的进行询问，这个方法相对就比较容易实行。当然，你可能必须做一些调查，判断一到两个前提正确与否。这里有一些清晰，完整陈述的论证：

** 论证 **
所有人都会死。苏格拉底是人。所以，苏格拉底会死。
问题
是不是所有人都会死？苏格拉底是人吗？这个结论是从前提中逻辑推导出来的吗？还可以得出其他类似的结论？

评论：前提很显然是对的。并且，做出的结论，也只有这个结论是符合逻辑的。因此，论证是有效的。

论证
任何包含强体力的活动都可以恰当的分类成一种运动。健美运动包括强体力活动。因此，健美运动可以被合适地分类成一种运动。
问题
有没有一种体力活很费力但不是体育运动？健美运动包含费力的身体运动吗？这个结论是从前提中逻辑推导出来的吗？还有没有其他合理的结论？

评论：即使第二个前提是正确的，从前提推导出来的结论也符合逻辑，因为第一个前提是错误的，因此结论是无效的。很多和体育运动毫无关系的体力活很费力——比如移动钢琴。注意，显示出这个论证无效并不能证明健美运动不应该分类为体育运动。或许其他的论证更好，可以证明是有效的。

论证
有罪的人通常不能通过测谎仪的测试。
布鲁诺没有通过测谎仪测试。
那么，布鲁诺有罪。
问题
（第一个前提）是真的吗？
他真的没有通过测试？
这个结论是从前提中逻辑推导出来的吗？还有没有其他合理的结论？

评论：第一和第二个前提都是真的。（权威人士可能会对布鲁诺的得分撒谎，但是我们假设他们没有这么做。）即使如此，这些前提也不能提供足够的证据得到给出来的结论，或者其他任何结论。我们要知道一个无辜的人是否会在测谎仪面前失败。如果这样，布鲁诺可能是无辜的

论证
成功只光顾努力工作的人。
简是成功人士。
那么，简工作努力。
问题
经常是这样吗？
简成功了吗？
这个结论是从前提中逻辑推导出来的吗？还有没有其他合理的结论？

评论
第一个前提并不完全正确，有些努力工作的人最终还是失败了，因为他们缺乏必要的才能或者背景经验去应对挑战。还有，有些不努力工作的人也成功了，因为他们有财富和/或者有影响力。即使我们承认第二个前提是正确的，因为第一个前提，这个论证也被判定为不合理。

你有没有这样的经验，你听到某个议题的论证，印象深刻，然后又听到相反的论证，印象更深刻？这种事情经常发生。比如，在2000年总统大选前的初次竞争中，候选人乔治布什早年间吸食可卡因的问题被揭发出来。有些评论员认为如果布什确实吸食过，那么他就是伪君子，因为他在德克萨斯州任州长的时候，签署过法令对可卡因使用者进行严厉惩罚。这个论证看上去很好。但是，其他的评论员认为一位曾经吸食过毒品的人改过自新后，比起其他从来没有碰过毒品的人更能够认清毒品对个人和社会的危害。他们辩称一个酒鬼比绝对禁酒者对于滥用酒精的害处更有权威性，一个改过自新的罪犯比一个遵守法律的公民对犯罪的罪恶更熟悉，等等。

请记住，当你能够听到双方意见，或者至少考虑对于议题某一方的人们对另一方观点的批判，你对任何论证的评价就有可能是最有效的。

原文：

Evaluating Arguments

The basic approach to evaluating arguments can be stated simply: Decide whether the premises are true or false and whether the reasoning that leads from them to the conclusion is valid. If both criteria are met, the argument is sound. When the argument is clearly and fully stated and you ask the right questions, this approach is relatively easy to follow. You may, of course, have to do some investigating to determine the truth or falsity of one or both premises. Here are some examples of clear, fully stated, arguments:

The Argument
All men are mortal. Socrates is a man. Therefore, Socrates is mortal.
The Questions
Are all men mortal? Is Socrates a man?
Does this conclusion follow logically from what is stated in the premises? Does any other conclusion follow equally well?

Comment: The premises obviously are true. Also, the conclusion offered, and only that conclusion, follows logically. Accordingly, the argument is sound.

The Argument
Any activity that involves physical exertion is properly classified as a sport.
Bodybuilding involves physical exertion.
Therefore, bodybuilding is properly classified as a sport.
The Questions
Are there any physical activities that are not a sport yet are physically strenuous?
Does bodybuilding involve physical exertion?
Does this conclusion follow logically from what is stated in the premises? Would
any other conclusion be as reasonable?

Comment: Even though the second premise is true and the conclusion follows logically from the premises, this argument is unsound because the first premise is false. Many physical activities are in no way related to a sport yet are physically strenuous—moving pianos, for example. Note that showing this argument to be unsound does not prove that bodybuilding should not be classified as a sport. Perhaps some other argument could be advanced that would prove to be sound.

The Argument
Guilty people usually fail lie detector tests.
Bruno failed his lie detector test. Therefore, Bruno is guilty.
The Questions
Is this true?
Did he really?
Does this conclusion follow logically from what is stated in the premises? Would
any other conclusion be as reasonable?

Comment: Both the first and the second premises are true. (The authorities could have lied about Bruno’s score, but let’s assume they didn’t.) Still, the premises don’t provide sufficient evidence to draw the conclusion that is given or, for that matter, any other conclusion. We need to know whether an innocent person can fail a lie detector test. If so, then Bruno could be innocent.

The Argument
Success comes to those who work hard.
Jane is successful.
Therefore, Jane worked hard.
The Questions
Does it always?
Is she?
Does this conclusion follow logically from what is stated in the premises? Would
any other conclusion be as reasonable?

Comment: The first premise is not entirely true. Some people who work hard end up failing anyway because they lack the necessary aptitude or background experience to meet the challenge. Moreover, some people who do not work hard succeed anyway because they have wealth and/or influence. Even if we grant that the second premise is true, the argument must still be judged unsound because of the first premise.

Did you ever have the experience of hearing an argument on some issue, being impressed with it, and then hearing the opposing argument and being even more impressed with that? It happens often. For example, in the primary battles prior to the 2000 presidential election, a question arose as to whether candidate George W. Bush had used cocaine many years earlier. Some pundits argued that if he had, then he was a hypocrite because as governor of Texas he signed into law a bill containing tough penalties for cocaine users. The argument sounded good. But then other pundits argued that a person who had used drugs but had learned to avoid them was in a better position to know their danger to individuals and society than one who had not. They reasoned that an alcoholic can speak more authoritatively than a teetotaler on the misuse of alcohol, a reformed criminal is more familiar with the evils of crime than a law-abiding citizen, and so on.

Remember that your evaluation of any argument is likely to be most effective when you are able to hear both sides or at least to consider the criticisms people on each side of the issue make of the other side’s view.