Tuesday, 3 September 2013

James Lett: A Field Guide to Critical Thinking

I have been using James Lett's field guide since I first read this article in 1990:


It is written in response to the prevalence of paranormal beliefs in the USA, and I have used it in negotiating the tangles and thickets and sinkholes and bogs in the belief systems of mental health care. 

Here is a distillation of James Lett's six  guidelines, that he calls FiLCHeRS: 

Falsifiability: It must be possible to conceive of evidence that would prove the claim false.
Logic: Any argument offered as evidence in support of any claim must be sound. An invalid argument can be recognize by the simple method of counterexample: If you can conceive of a single imaginable instance whereby the conclusion would not necessarily follow from the premises even if the premises were true, then the argument is invalid.
Comprehensiveness: The evidence offered in support of any claim must be exhaustive — that is all of the available evidence must be considered.
Honesty: The evidence offered in support of any claim must be evaluated without self-deception.The rule of honesty is a corollary to the rule of comprehensiveness. When you have examined all of the evidence, it is essential that you be honest with yourself about the results of that examination. If the weight of the evidence contradicts the claim, then you are required to abandon belief in that claim. The obverse, of course, would hold as well.
Replicability: If the evidence for any claim is based upon an experimental result, or if the evidence offered in support of any claim could logically be explained as coincidental, then it is necessary for the evidence to be repeated in subsequent experiments or trials.
Sufficiency: The evidence offered in support of any claim must be adequate to establish the truth of that claim, with these stipulations: the burden of proof for any claim rests on the claimant, extraordinary claims demand extraordinary evidence,  and evidence based upon authority and/or testimony is always inadequate 

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