證據(jù)是什么？

陳述觀點就是告訴其他人你關(guān)于某事的想法；展示證據(jù)就是告訴其他人我們的想法是有意義的。表達(dá)比被告知更加有趣和印象深刻——我們在學(xué)校就知道這些了。那么，為什么，還有那么多文章和演講由一個又一個觀點堆積，但是卻幾乎沒有證據(jù)支持它們。就像我們在第五章看到的，一個原因是人類的大腦是一個名副其實的觀點工廠，所以絕大多數(shù)人都有大量的意見分享。另一個原因是人們傾向于只記得觀點，而忘記了獲得它們的經(jīng)過，就好像學(xué)生在忘記了他們的考試和作業(yè)分?jǐn)?shù)后很長時間還記得他們最后課程的等級。

在某種更意味深長的角度看，另一個原因是有時候很少有或者根本沒有證據(jù)可以想起來——換句話說，觀點根本沒有任何實質(zhì)性基礎(chǔ)。例如，在1999年早期人們認(rèn)為（William Jefferson Clinton’）克林頓在法庭宣誓后撒謊沒有“上升到被彈劾的程度”。當(dāng)被問道為什么這么想的時候，有些人用同樣的或者類似的話重復(fù)他們的論斷：“他不應(yīng)該因為這些事情被趕出白宮”或者“這是他和希拉里的事情”。還有些人提供相關(guān)聯(lián)的觀點：“這是右翼的陰謀”或者“獨立的檢察官肯尼斯斯塔爾（Kenneth Starr）在進(jìn)行政治迫害”。雖然無法確定他們?yōu)槭裁催@么想這么做，他們用幾乎一樣的措辭表達(dá)觀點，而這些觀點是半打白宮顧問和無數(shù)其他克林頓的支持者不斷重復(fù)的觀點。這個事實表明了這些人只是簡單地不經(jīng)評估地接受了別人的觀點。

我們都能認(rèn)同這些人。我們絕大多數(shù)不想承認(rèn)，當(dāng)我們要找到理由支持觀點時，我們會制造出最站不住腳的證據(jù)。我們可能會安慰自己說我們腦袋里有厚厚一疊證明文件沒有整理好。但是非?？赡艿氖虑槭沁@個毫無價值的證據(jù)就是我們的所有。批判性思考者被誘惑犯下同樣的自我欺騙的錯誤，這些錯誤給其他人帶來了麻煩，但是他們學(xué)到了抵制這些誘惑的價值。更重要的是，他們養(yǎng)成了在形成觀點前核實證據(jù)的質(zhì)量和數(shù)量的習(xí)慣。并且，他們在表達(dá)觀點前重新復(fù)核證據(jù)。這樣花費(fèi)時間所獲得的補(bǔ)償遠(yuǎn)大于因為知道自己在說什么的信心。

證據(jù)的種類

評估你自己和其他人的觀點，你就需要理解不同種類的證據(jù)。這需要知道不同種類證據(jù)的價值和局限性，還有如何問合適的問題。最重要的證據(jù)有個人經(jīng)驗、未發(fā)表的報告、已發(fā)表的報告、目擊證人證言、名人證言、專家意見、實驗、統(tǒng)計、調(diào)查、正式觀察和研究綜述。
特別需要注意的是，這里的安排不是按可靠性的升序或降序排列，而是按熟悉程度的大致順序排列——個人經(jīng)驗對大多數(shù)人來說非常熟悉，研究綜述則不太熟悉。

原文：

What Is Evidence?

To state an opinion is to tell others what we think about something; to present evidence is to show others that what we think makes sense. Being shown is much more interesting and impressive than being told—we’ve all known this since grade school. Why, then, does so much writing and speaking consist of piling one opinion on another, with little or no evidence offered in support of any of them? As we saw in Chapter 5, one reason is that the human mind is a veritable opinion factory, so most people have an abundance of opinions to share. Another reason is that people tend to remember their opinions and forget the process by which they got them, much as students remember their final grade in a course long after they have forgotten the tests and homework grades that resulted in it.

Another, and in some ways more significant, reason is that sometimes there is little or no evidence to remember—in other words, the opinion is based on nothing substantial. For example, in early 1999 many people held the opinion that William Jefferson Clinton’s lying under oath did not “rise to the level of an impeachable offense.” When asked to explain why they thought that, some people repeated the assertion in identical or similar words: “He shouldn’t be removed from office for what he did” or “It’s between him and Hillary.” Some offered related opinions: “It’s a right-wing conspiracy” or “Independent counsel Kenneth Starr is on a witch-hunt.” Though it is impossible to be certain why they thought as they did, the fact that they expressed the opinion in the very same words incessantly repeated by a half dozen White House advisors and innumerable other Clinton supporters suggests that they simply borrowed the opinion without evaluating it.*

We can all identify with those people. More often than most of us would care to admit, when called on to support our opinions, we manage to produce only the flimsiest of evidence. We may soothe ourselves with the notion that a thick folder of evidence lies misfiled in our minds, but the very real possibility remains that flimsy evidence was all we ever had. Critical thinkers are tempted to commit the same self-deception that plagues others, but they have learned the value of resisting that temptation. More important, they have developed the habit of checking the quality and quantity of the evidence before forming an opinion. Also, they review their evidence before expressing an opinion. The extra time this takes is more than compensated for by the confidence that comes from knowing what they are talking about.

Kinds of Evidence

To evaluate your own and other people’s opinions, you will need to understand the various kinds of evidence. This entails knowing the value and limitations of each kind, as well as the appropriate questions to ask. The most important kinds of evidence are personal experience, unpublished report, published report, eyewitness testimony, celebrity testimony, expert opinion, experiment, statistics, survey, formal observation, and research review.
It is important to note that the arrangement here is not in ascending or descending order of reliability but rather in rough order of familiarity— with personal experience being very familiar to most people and research review much less familiar.