How Good Is the Evidence？
Summary
In these two chapter, we begin the process of evaluating factual claims by asking critical questions.
Almost all reasoning we encounter includes beliefs about the world that the communicator wants us to accept as “facts” in the forms of conclusions, reasons, or assumptions. Such beliefs are referred as factual claims.
On encountering a factual claim, we should ask the following questions:
“Why should I believe it?”
“Does the claim need evidence to support it?”
If it does, and if there is no evidence, the claim is a mere assertion. We should seriously question its dependability!
If there is evidence, our next question is, “How good is the evidence?”
In essence, we want to ask, “Can we count on such beliefs?”
The greater the quality and quantity of evidence supporting a claim, the more we can depend on it and consider the claim as a fact. We also need to know which factual claims are most dependable. By asking questions related to proofs and evidences, we can have a better knowledge of both the support for the claims and the dependability of the arguments. When the claim is adequately supported by solid evidence, we accept a factual claim as dependable.
Major Kinds of Evidence
✓ intuition
Intuition can be dependable if supported by solid evidence
✓ personal experiences
Personal experiences may be dangerous and not reliable.
Fallacy: Hasty Generalization: A person draws a conclusion about a large group based on experiences with only a few members of the group.
✓ case examples
Case examples are helpful because they demonstrate important possibilities and put a personal face on abstract statistics.
✓ testimonials
Testimonials are not helpful and we should be wary of its problems, including people's selectivity, personal interests, some omitted information and any other human factors.
✓ appeals to authorities or experts
Appeals to authorities or experts, which may have a strong personal feeling, are not always correct, but should be taken seriously due to its cautiousness.
✓ personal observations
Personal observation is a valuable kind of evidence but has a great chance to be biased if it contains personal judgement or expectation.
✓ research studies
Research study is one of our best sources of evidence if conducted well, because it emphasizes replication, control, and precision.
But it is not perfect. Its flaws are listed as follows：
1. Research varies greatly in quality.
2. Many research findings contradict one another.
3. Research findings sometimes do not prove conclusions.
4. Researchers expectations, attitudes, values, needs and the way they conduct the research, interpret their research findings may lead to various results.
5. Speakers and writers often distort or simplify research conclusions.
6. Research “facts” change over time, especially claims about human behavior.
7. Research varies in how artificial it is.
8. The need for financial gain, status, security, and other factors can affect research outcomes and selection of which studies will be published.
Fallacy: Impossible Certainty: Assuming that a research conclusion should be rejected if it is not absolutely certain.
Attention:
1. We can generalize only to people and events that are like those that we have studied in the research.
2. We cannot assume that survey responses accurately reflect true attitudes.
✓ analogies
Analogies both stimulate insights and deceive us. We need to process them critically.
Evidence is explicit information shared by the communicator that is used to back up or to justify the dependability of a factual claim. In prescriptive arguments, evidence will be needed to support reasons that are factual claims; in descriptive arguments, evidence will be needed to directly support a descriptive conclusion.
Thought
作者讲到这里其实讲得也很清楚了，批判性思考的核心就是不断质疑，即便是权威也勿忘质疑，阅读时可以质疑的要点有问题、论证、结论、理由、描述与猜测。难点在于我们可以质疑哪些方面。读者可能知道质疑的重要性，却难以面面俱到，有时漏了些因素，就难以提出批判性问题了。
本书第八章第九章的给我的启发就是影响篇章内容可信度各个方面都非常有道理。作者的确会有这样或那样的问题，也会使用各种方法引导读者走向自己的结论和判断，有些走向也是我始料未及的。我在阅读的过程中有时会质疑，但并不会思考得如此细致和全面，下次再对文章内容有想法的时候，我倒是也可以参照一下这两章学习到的方法和技巧了。