Back-of-the-envelope calculation: a possible explanation to a problem occurs to you, you pull out an old envelope, appeal to your knowledge of fundamental physics, scribble a few approxi­mate equations on the envelope, substitute in likely numerical values, and see if your answer comes anywhere near explaining your problem. If not, you look for a different explanation. It cut through nonsense like a knife through butter.

Edmund Way Teale in his 1950 book Circle of the Seasons understood the dilemma better: It is morally as bad not to care whether a thing is true or not, so long as it makes you feel good, as it is not to care how you got your money as long as you have got it.

Pseudoscience speaks to powerful emotional needs that science often leaves unfulfilled.

Is it possible that people in all times and places occasionally experience vivid, realistic hallucinations, often with sexual content, about abduction by strange, telepathic, aerial creatures who ooze through walls, with the details filled in by the prevailing cultural idioms, sucked out of the Zeitgeist? Others, who have not personally had the experience, find it stirring and in a way familiar. They pass the story on. Soon it takes on a life of its own, inspires others trying to understand their own visions and halluci­nations, and enters the realm of folklore, myth and legend. The connection between the content of spontaneous temporal lobe hallucinations and the alien abduction paradigm is consistent with such a hypothesis.

Hypnosis is an unreliable way to refresh memory. It often elicits imagination, fantasy and play as well as true recollections, with neither patient nor therapist able to distinguish the one from the other. Hypnosis seems to involve, in a central way, a state of heightened suggestibility. Courts have banned its use as evidence or even as a tool of criminal investiga­tion. The American Medical Association calls memories surfacing under hypnosis less reliable than those recalled without it.

'Memories of an event more closely resemble a story undergoing constant revision than a packet of pristine information'.

It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.
— Sherlock Holmes, in Arthur Conan Doyle's A Scandal in Bohemia (1891)

[Some of] the most common and perilous fallacies of logic and rhetoric:

• Absence of evidence is not evidence of absence.
• Observational selection, also called the enumeration of favourable circumstances, or as the philosopher Francis Bacon described it, counting the hits and forgetting the misses.
• Non sequitur - Latin for 'it doesn't follow' (e.g., our nation will prevail because God is great. But nearly every nation pretends this to be true; the German formulation was 'Gott mil uns'). Often those falling into the non sequitur fallacy have simply failed to recognize alternative possibilities.
• Post hoc, ergo propter hoc - Latin for 'it happened after, so it was caused by' (e.g. before women got the vote, there were no nuclear weapons).
• Excluded middle, or false dichotomy - considering only the two extremes in a continuum of intermediate possibilities (e.g., 'sure, take his side; my husband's perfect; I'm always wrong.' Or: 'either you love your country or you hate it.' Or: 'if you're not part of the solution, you're part of the problem').
• Straw man – caricaturing a position to make it easier to attack (e.g., scientists suppose that living things simply fell together by chance – a formulation that wilfully ignores the central Darwin­ian insight, that Nature ratchets up by saving what works and discarding what doesn't. Or – this is also a short-term/long-term fallacy – environmentalists care more for snail darters and spotted owls than they do for people).

One of the saddest lessons of history is this: if we've been bamboozled long enough, we tend to reject any evidence of the bamboozle. We're no longer interested in finding out the truth. The bamboozle has captured us. It's simply too painful to acknowledge, even to ourselves, that we've been taken. Once you give a charlatan power over you, you almost never get it back. So the old bamboozles tend to persist as the new ones rise.

It's sometimes easier to reject strong evidence than to admit that we've been wrong.

Why does it matter what biases and emotional predispositions scientists bring to their studies, so long as they are scrupulously honest and other people with different proclivities check their results?

Science is different from many another human enterprise - not, of course, in its practitioners' being influenced by the culture they grew up in, nor in sometimes being right and sometimes wrong (which are common to every human activity), but in its passion for framing testable hypotheses, in its search for definitive experiments that confirm or deny ideas, in the vigour of its substantive debate, and in its willingness to abandon ideas that have been found wanting. If we were not aware of our own limitations, though, if we were not seeking further data, if we were unwilling to perform controlled experiments, if we did not respect the evidence, we would have very little leverage in our quest for the truth. Through opportunism and timidity we might then be buffeted by every ideological breeze, with nothing of lasting value to hang on to.

Ignorance more frequently begets confidence than does knowledge: it is those who know little, and not those who know much, who so positively assert that this or that problem will never be solved by science.
— Charles Darwin, Introduction, The Descent of Man (1871)

Societies that teach contentment with our present station in life, in expectation of post mortem reward, tend to inoculate themselves against revolution. Further, fear of death, which in some respects is adaptive in the evolutionary struggle for existence, is maladaptive in warfare. Those cultures that teach an afterlife of bliss for heroes - or even for those who just did what those in authority told them - might gain a competitive advantage.

At the heart of science is an essential balance between two seemingly contradictory attitudes - an openness to new ideas, no matter how bizarre or counterintuitive, and the most ruthlessly sceptical scrutiny of all ideas, old and new. This is how deep truths are winnowed from deep nonsense. The collective enterprise of creative thinking and sceptical thinking, working together, keeps the field on track. Those two seemingly contradictory attitudes are, though, in some tension.

[…] the Iliad and the Odyssey, literary masterpieces that are themselves the epitome of liberal rational thinking.

In the history of ancient Greece, we can see nearly all significant events driven by the caprice of the gods in Homer, only a few events in Herodotus, and essentially none at all in Thucydides. In a few hundred years, history passed from god-driven to human-driven.

Of Cromer's criteria for 'objective thinking', we can certainly find in hunter-gatherer peoples vigorous and substantive debate, direct participatory democracy, wide-ranging travel, no priests, and the persistence of these factors not for 1,000 but for 300,000 years or more. By his criteria hunter-gatherers ought to have science. I think they do. Or did.

(And while requiring calculus, the most consistently exciting, provocative and inspiring science popularization of the last few decades seems to me to be Volume I of Richard Feynman's Introductory Lectures on Physics.)

Cutting off fundamental, curiosity-driven science is like eating the seed corn. We may have a little more to eat next winter, but what will we plant so we and our children will have enough to get through the winters to come?

Ubi dubium ibi libertas: Where there is doubt, there is freedom.
— Latin proverb

Part of the duty of citizenship is not to be intimidated into conformity.

In his celebrated little book, On Liberty, the English philosopher John Stuart Mill argued that silencing an opinion is 'a peculiar evil'. If the opinion is right, we are robbed of the 'opportunity of exchanging error for truth'; and if it's wrong, we are deprived of a deeper understanding of the truth in 'its collision with error'. If we know only our own side of the argument, we hardly know even that; it becomes stale, soon learned only by rote, untested, a pallid and lifeless truth. Mill also wrote, 'If society lets any considerable number of its members grow up as mere children, incapable of being acted on by rational consideration of distant motives, society has itself to blame.' Jefferson made the same point even more strongly: 'If a nation expects to be both ignorant and free in a state of civilization, it expects what never was and never will be.' In a letter to Madison, he continued the thought: 'A society that will trade a little liberty for a little order will lose both, and deserve neither.'