Principles of Skepticism

I was flicking through one of the most useful books I own, How to Think About Weird Things - Critical Thinking for a New Age (2nd Ed), by Theodore Schick, Jr. and Lewis Vaughn, and I thought I'd post these "Principles of Skepticism" from their book. They say they are:

Explanations of thirty-four principles of knowledge, reasoning and evidence that you can use to enhance your problems-solving skills and sharpen your judgement.

I highly recommend their book to you to get the full story behind these principles. Schick and Vaughn expand upon them with many great examples. However, most of them are fairly self explanatory. Note that these principles are rational rules of thought to help one form an informed position on a topic. The topics are essentially any claim about the physical world we live in - anything that can cause an effect in the physical world. This is applicable to all the claims of science and psuedoscience. Scientific claims They don't guarantee that you'll be correct. However, they dramatically decrease the likelihood of you being incorrect. Most importantly, being good at analysing propositions is fun! I've broken them up under the titles of the chapters of the book they appear in, so they'll make sense:

Chapter 2 - The Possibility of the Impossible

1) Just because something is logically possible doesn't mean that it's real.

2) Just because a claim hasn't been conclusively refuted doesn't mean that it's true.

3) Just because a claim hasn't been conclusively proven doesn't mean that it's false.

4) Just because you can't explain something doesn't mean that it's supernatural.

5) Just because something is physically possible doesn't mean that it's real.

Chapter 3 - Looking for Truth in Personal Experience:

6) Just because something seems (feels, appears) real doesn't mean that it is.

7) It's reasonable to accept personal experience as reliable evidence only if there's no reason to doubt its reliability.

Chapter 4 - Relativism, Truth and Reality:

8) Just because you believe that something is true doesn't mean that it is.

9) Just because a group of people believe that something is true doesn't mean that it is.

10) There are objective truths.

Chapter 5 - Knowledge, Belief and Evidence:

11) We are justified in believing a proposition when we have no good reason to doubt it.

12) There is good reason to doubt a proposition if it conflicts with other propositions we have good reason to believe.

13) The more background information a proposition conflicts with, the more reason there is to doubt it.

14) When there is good reason to doubt a proposition, we should proportion our belief to the evidence.

15) There is good reason to doubt a proposition if it conflicts with expert opinion.

16) Just because someone is an expert in one field doesn't mean that he or she is an expert in another.

17) If we have no reason to doubt what's disclosed to us through perception, introspection, memory, or reason, then we're justified in believing it.

Chapter 6 - Evidence and Inference:

18) When evaluating a claim, look for disconfirming as well as confirming evidence.

19) When evaluating a claim, look at all the relevant evidence, not just the psychologically available evidence.

Chapter 7 - Science and Its Pretenders:

20) A hypothesis is scientific only if it is testable, that is, only if it predicts something other than what it was introduced to explain.

21) Other things being equal, the best hypothesis is the one that is the most fruitful, that is, makes the most novel predictions.

22) Other things being equal, the best hypothesis is the one that has the greatest scope, that is, that explains and predicts the most diverse phenomena.

23) Other things being equal, the best hypothesis is the simplest one, that is, the one that makes the fewest assumptions.

24) Other things being equal, the best hypothesis is the one that is the most conservative, that is, the one that fits best with established beliefs.

25) We should accept an extraordinary hypothesis only if no ordinary one will do.

Chapter 8 - How to Assess a "Miracle Cure":

26) Personal experience alone generally cannot establish the effectiveness of a treatment beyond a reasonable doubt.

27) Case studies alone generally cannot establish the effectiveness of a treatment beyond a reasonable doubt.

28) When claims of a treatment's effectiveness are based solely on case studies or personal experience, you generally cannot know that the treatment is effective.

29) Scientific evidence gained through controlled experiments - unlike personal experience and case studies - generally can establish the effectiveness of a treatment beyond a reasonable doubt.

30) Single medical studies generally cannot establish the effectiveness of a treatment beyond a reasonable doubt.

31) When the results of relevant studies conflict, you cannot know that the treatment in question is effective.

32) New study results that conflict with well-established findings cannot establish the effectiveness of a treatment beyond a reasonable doubt.

33) Test-tube studies alone generally cannot establish the effectiveness of a treatment beyond a reasonable doubt.

34) Animal studies alone generally cannot establish the effectiveness of a treatment beyond a reasonable doubt.

35) Observational studies alone generally cannot establish the effectiveness of a treatment beyond a reasonable doubt.

36) Clinical trials with any of these limitations - lack of a control group, a faulty comparison between experimental and control group, and a small number of subjects (a pilot study) - generally cannot establish the effectiveness of a treatment beyond a reasonable doubt.