From Sagan, Carl. 1996. The Demon - Haunted World. Ballantine Books. New York.

To exercise

The contents of Sagan's toolbox:

Independent confirmation of facts:
In science, observations need to be both repeatable, and repeated.

Substantive debate by knowledgeable proponents of all points of view:
No good comes when an authority silences substantive debate on an issue.

There are no true authority figures:
Scientific discourse takes place on a level playing field in which ideas are judged by their merits. Dr. Holtz saw this bathroom graffito which sums it all up: "Ideas by merit, not by source."

Use more than one hypothesis:
There are often many possible patterns or explanations for patterns. They should all be examined, and the quickest way to get to the answer is usually to examine them simultaneously.

Don't get too attached to your hypotheses:
The whole point of testing a hypothesis is to try to falsify it. If we don't try in earnest, then we really haven't done much.

Quantify:
Remember, subjective observations are useless to science. Often, the difference between subjectivity and objectivity is the ability to count or measure. So, count and measure.

A chain is as strong as its weakest link:
When your argument requires a chain of logical steps, each step must be valid or the whole thing is hogwash.

Parsimony (aka Occam's Razor):
When there are more than one possible solution, the simplest one will usually be correct.

And the really big one, Falsifiability:
It must be possible, in principle, to know if your hypothesis is wrong. If you have no way of knowing if you are wrong, there's really not much to test or discuss scientifically.

Twenty Common Logical Fallacies:

The ad hominem argument:
Ad hominem means "at the person." Ad hominem arguments are those that attack a person making an argument without touching the argument itself.

Appeals to ignorance:
In effect, this argument boils down to "I can't imagine how something took place, so therefore it didn't take place." Sometimes, this is used if the underlying processes behind an event are poorly known. The problem, of course, is that we can't say something didn't happen just because we don't know everything about how it happened.

Arguments from adverse consequences:
These are arguments in which one is asked not to accept a position because doing so would require them to accept unpleasant consequences that stem from it.

The Argument from Authority:
The idea that we should adopt an idea because some respected person tells us to. This is extremely common in advertising, where a spokesperson is chosen to advocate a product on the basis of popularity or perceived expertise.

Begging the question:
Essentially, assuming the answer to a question when posing it.

Correlation equals causation:
It's easy to be convinced that because two things happen simultaneously, one must cause the other. This is not something we can assume. The hypothesis of non-correlation has to be tested.

The disregarded middle:
In the real world, there is often a broad spectrum of possible opinion on a given topic. A serious fallacy is to assume the only possible positions are the two extremes.

Inconsistency:
Employing different observational methods or criteria of falsification or proof when only one is required.

Meaningless question:
Attempting logically to analyze an issue that makes no sense.

Non-comprehension of statistics:
There's nothing to add to this one.

Non-sequitur:
This is Latin for "It doesn't follow." We apply the term to cases where someone presents two unconnected ideas as if one were a logical consequence of the other.

Observational selection:
Noticing only the observations that tend to form the patterns that one wants to see and ignoring those that either don't fit of form undesirable patterns.

Post hoc ergo propter hoc:
This is Latin for "it came after so it was caused by..." This is a special case of the correlation = causation fallacy in which when one event follows another it is claimed to have been caused by it.

The slippery slope:
The logical equivalent of the game of "gossip," in which a message is transmitted from one person to the next, accumulating distortions and errors as it goes. The slippery rope is the irrational fear that by accepting a valid argument you will be drawn in turn toward similar, but less valid ones, until you are persuaded to accept completely unacceptable arguments.

Special pleading:
Artificial resuscitation for an argument that has already been falsified by some reasonable standard. This usually assumes the form of an argument that the special circumstances surrounding a particular situation invalidate the falsification.

Statistics of small numbers:
Attempting to infer a large pattern from too few observations.

Straw Man:
The straw man argument is one in which a weak substitute for opposing position is created, then the substitute is flamboyantly attacked and torn to shreds. If the deception is successful, listeners never notice that the substitution occurred and imagine that the original argument was defeated.

Suppressed evidence or half truths:
Unconscious or willful failure to consider relevant data.

Weasel Words:
This is similar to the straw man. Here, one deceives the listener by subtly replacing words or terms that the listener is sure to object to with unfamiliar terms that do not call forth the same negative emotions.

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