I’m enjoying Carl Sagan’s classic The Demon Haunted World at the minute and just read the chapter on The Fine Art of Baloney Detection. I thought that his toolkit for sceptical thinking was so good that I’d post a paraphrased version:
- Wherever possible there must be independent confirmation of the "facts".
- Encourage substantive debate on the evidence by knowledgeable proponents of all points of view.
- Arguments from authority carry little weight - "authorities" have made mistakes in the past.
- Spin more than one hypothesis. If you think of all the solutions (or as many as you can) and try to find systematic ways of disproving them, rather than just running with the first idea that came to mind, you are much more likely of getting to the right answer.
- Try not to get overly attached to a hypothesis just because it's yours. See if you can find reasons for rejecting it. If you don't, others will.
- Quantify. If whatever it is you're explaining has some measure, some numerical quantity attached to it, you'll be much better able to discriminate among competing hypotheses.
- If there's a chain of argument, every link in the chain must work (including the premise) - not just most of them.
- Apply Occam's Razor: "other things being equal, a simpler explanation is better than a more complex one."
- Always ask whether the hypothesis can be, at least in principle, falsified. Propositions that are untestable, unfalsifiable are not worth much: You must be able to check assertions out.
Things to avoid:
- Ad hominem arguments – attack the argument, not the man (or woman).
- Arguments from authority – just because you might be in a position of authority, doesn't mean you’re right.
- Arguments from adverse consequences - something like ‘the theory of evolution leads can lead to eugenics, therefore the theory of evolution is wrong or ‘bad’.
– absence of evidence is not evidence of absence; just because it hasn’t been proved to be false, doesn’t mean it’s true.
- Special pleading – ‘God moves in mysterious ways’ or ‘We’ll never know how or why god does what he does’ is not an answer.
- Begging the question (or assuming the answer) – Sagan’s example is one of the best: ‘We must institute the death penalty to discourage violent crime’ assumes that having the death penalty does in fact cause crime to fall – see all the states in America for examples of how this isn’t true.
- Observational selection (or ‘cherry-picking’) – Don’t count the hits and forget the misses.
- Misunderstanding the statistics of small numbers - “I’ve thrown three sevens in a row. Tonight I can’t lose.”
- Misunderstanding the nature of statistics – Sagan illustrates this with one of my favourite examples of statsfail, ever: “President Eisenhower
expressing his astonishment and alarm on discovering that fully half of all Americans have below average intelligence.”
- Inconsistency – E.g. Considering it reasonable for the Universe to exist forever into the future, but judge absurd the possibility that it has infinite duration in the past.
- Non-sequiters – E.g. Our nation will prevail because God is great.
- Post hoc, ergo propter hoc (Latin for ‘it happened after so it was caused by’) – see pretty much every piece of ‘evidence’ touted by anti-vaccine, alt-med anti-science types.
- Meaningless questions – E.g. 'What happens when an irresistible force meets an immovable object? Trying to answer a question like that teaches us nothing.
- False dichotomies, or the excluded middle – considering only the two extremes in a continuum of possibilities. This fallacy is related to creating short-term vs. long-term dichotomies, for example ‘Why explore space or pursue fundamental science when we have so huge a budget deficit’. (Sagan wrote this book 15 years ago but given the fragile state of the world economy this sad sentiment rings truer with a lot of people now more than ever).
Slippery slope – Again Sagan’s example of this fallacy, that if we allow abortion in the first weeks of pregnancy that it will be impossible to prevent the killing of a full-term infant, is distressingly persistent in some fundamentalist Christian circles.
- Confusing correlation with causation. It is wrong to assume that that because two things or events occur together, one must be the cause of the other.
- Straw man – caricaturing a position to make it easier to attack. An example I like People against unions are against the working class.
- Suppressed evidence or half-truths – it's sneaky and wrong.
- Weasel words – creating an impression that something specific and meaningful has been said, when in fact only a vague or ambiguous claim, or even a refutation has been communicated. Sagan uses are cracking quote from Talleyrand “An important art of politicians is to find new names for institutions which under old names have become odious to the public.”
Here's the brilliant Micheal Shermer's own take on skepticism as a Baloney Detection Kit: