Carl Sagan’s book “The Demon-Haunted World: Science as a candle in the dark” includes ideas and tools for skeptical thinking.
The following are recommended as tools for testing arguments and detecting fallacious or fraudulent reasoning:
(1) Wherever possible there must be independent confirmation of the facts.
(2) Encourage substantive debate on the evidence by knowledgeable proponents of all points of view.
(3) Arguments from authority carry little weight (in science there are no “authorities”).
They will do so again in the future. Perhaps a better way to say it is that in science there are no authorities; at most, there are experts.
(4) Spin more than one hypothesis – don’t simply run with the first idea that caught your fancy.
If there’s something to be explained, think of all the different ways in which it could be explained. Then think of tests by which you might systematically disprove each of the alternatives. What survives, the hypothesis that resists disproof in this Darwinian selection among “multiple working hypotheses,” has a much better chance of being the right answer than if you have simply run the with first idea that caught your fancy.
(5) Try not to get overly attached to a hypothesis just because it’s yours.
It’s only a way station in the pursuit of knowledge. Ask yourself why you like the idea. Compare it fairly with the alternatives. See if you can find reasons for rejecting it. If you don’t, others will.
(6) Quantify, wherever possible.
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. What is vague and qualitative is open to many explanations. Of course there are thruths to be sought in the many qualitative issues we are obliged to confront, but finding them is more challenging.
(7) If there is a chain of argument every link in the chain must work.
(8) Occam’s razor.
If there are two hypothesis that explain the data equally well choose the simpler.
(9) Ask whether the hypothesis can, at least in principle, be falsified (ie. shown to be false by some unambiguous test). In other words, it is testable? Can others duplicate the experiment and get the same result?
Propositions that are untestable, unfalsifiable are not worth much. Consider the grand idea that our Universe and everything in it is just an elementary particle – an electron, say – in a much bigger Cosmos.