But rather than preaching from the ivory tower of self-righteousness, Sagan approaches the subject from the most vulnerable of places — having just lost both of his parents, he reflects on the all too human allure of promises of supernatural reunions in the afterlife, reminding us that falling for such fictions doesn’t make us stupid or bad people, but simply means that we need to equip ourselves with the right tools against them.

Through their training, scientists are equipped with what Sagan calls a “baloney detection kit” — a set of cognitive tools and techniques that fortify the mind against penetration by falsehoods.

The kit is brought out as a matter of course whenever new ideas are offered for consideration. If the new idea survives examination by the tools in our kit, we grant it warm, although tentative, acceptance. If you’re so inclined, if you don’t want to buy baloney even when it’s reassuring to do so, there are precautions that can be taken; there’s a tried-and-true, consumer-tested method.

But the kit, Sagan argues, isn’t merely a tool of science — rather, it contains invaluable tools of healthy skepticism that apply just as elegantly, and just as necessarily, to everyday life. By adopting the kit, we can all shield ourselves against clueless guile and deliberate manipulation. Sagan shares 9 of these tools:

Just as important as learning these helpful tools, however, is unlearning and avoiding the most common pitfalls of common sense. Reminding us of where society is most vulnerable to those, Sagan writes:

“In addition to teaching us what to do when evaluating a claim to knowledge, any good baloney detection kit must also teach us what not to do. It helps us recognize the most common and perilous fallacies of logic and rhetoric. Many good examples can be found in religion and politics, because their practitioners are so often obliged to justify two contradictory propositions.”

Sagan admonishes against the 20 most common and perilous of these fallacies of logic and rhetoric— many rooted in our chronic discomfort with ambiguity — with examples of each in action:

Latin for “to the man,” attacking the arguer and not the argument.

e.g., The Reverend Dr. Smith is a known Biblical fundamentalist, so her objections to evolution need not be taken seriously

e.g., President Richard Nixon should be re-elected because he has a secret plan to end the war in Southeast Asia — but because it was secret, there was no way for the electorate to evaluate it on its merits; the argument amounted to trusting him because he was President: a mistake, as it turned out.

e.g., A God meting out punishment and reward must exist, because if He didn’t, society would be much more lawless and dangerous — perhaps even ungovernable. Or: The defendant in a widely publicized murder trial must be found guilty; otherwise, it will be an encouragement for other men to murder their wives.

The claim that whatever has not been proved false must be true, and vice versa.

e.g., There is no compelling evidence that UFOs are not visiting the Earth; therefore UFOs exist — and there is intelligent life elsewhere in the Universe. Or: There may be seventy kazillion other worlds, but not one is known to have the moral advancement of the Earth, so we’re still central to the Universe.) This impatience with ambiguity can be criticized in the phrase: absence of evidence is not evidence of absence.

… often to rescue a proposition in deep rhetorical trouble.

e.g., How can a merciful God condemn future generations to torment because, against orders, one woman induced one man to eat an apple? Special plead: you don’t understand the subtle Doctrine of Free Will. Or: How can there be an equally godlike Father, Son, and Holy Ghost in the same Person? Special plead: You don’t understand the Divine Mystery of the Trinity.

Also called assuming the answer.

e.g., We must institute the death penalty to discourage violent crime. But does the violent crime rate in fact fall when the death penalty is imposed? Or: The stock market fell yesterday because of a technical adjustment and profit-taking by investors — but is there any independent evidence for the causal role of “adjustment” and profit-taking; have we learned anything at all from this purported explanation?

Also called the enumeration of favorable circumstances, or as the philosopher Francis Bacon described it, counting the hits and forgetting the misses.

e.g., A state boasts of the Presidents it has produced, but is silent on its serial killers.

A close relative of observational selection.

e.g., They say 1 out of every 5 people is Chinese. How is this possible? I know hundreds of people, and none of them is Chinese. Yours truly. Or: I’ve thrown three sevens in a row. Tonight I can’t lose.

e.g., President Dwight Eisenhower expressing astonishment and alarm on discovering that fully half of all Americans have below average intelligence.

e.g., Prudently plan for the worst of which a potential military adversary is capable, but thriftily ignore scientific projections on environmental dangers because they’re not “proved.”Or: Attribute the declining life expectancy in the former Soviet Union to the failures of communism many years ago, but never attribute the high infant mortality rate in the United States (now highest of the major industrial nations) to the failures of capitalism.

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 mit uns”). Often those falling into the non sequitur fallacy have simply failed to recognize alternative possibilities.

Latin for “It happened after, so it was caused by”

e.g., Jaime Cardinal Sin, Archbishop of Manila: “I know of … a 26-year-old who looks 60 because she takes [contraceptive] pills.” Or: Before women got the vote, there were no nuclear weapons.

e.g., What happens when an irresistible force meets an immovable object? But if there is such a thing as an irresistible force there can be no immovable objects, and vice versa.

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”).

A subset of the excluded middle, but so important I’ve pulled it out for special attention.

e.g., We can’t afford programs to feed malnourished children and educate pre-school kids. We need to urgently deal with crime on the streets. Or: Why explore space or pursue fundamental science when we have so huge a budget deficit?

Related to (14) excluded middle.

e.g., If we allow abortion in the first weeks of pregnancy, it will be impossible to prevent the killing of a full-term infant. Or, conversely: If the state prohibits abortion even in the ninth month, it will soon be telling us what to do with our bodies around the time of conception.

e.g., A survey shows that more college graduates are homosexual than those with lesser education; therefore education makes people gay. Or: Andean earthquakes are correlated with closest approaches of the planet Uranus; therefore — despite the absence of any such correlation for the nearer, more massive planet Jupiter — the latter causes the former.

Caricaturing a position to make it easier to attack.

e.g., Scientists suppose that living things simply fell together by chance— a formulation that willfully 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.

e.g., An amazingly accurate and widely quoted “prophecy” of the assassination attempt on President Reagan is shown on television; but — an important detail — was it recorded before or after the event? Or: These government abuses demand revolution, even if you can’t make an omelette without breaking some eggs. Yes, but is this likely to be a revolution in which far more people are killed than under the previous regime? What does the experience of other revolutions suggest? Are all revolutions against oppressive regimes desirable and in the interests of the people?

e.g., The separation of powers of the U.S. Constitution specifies that the United States may not conduct a war without a declaration by Congress. On the other hand, Presidents are given control of foreign policy and the conduct of wars, which are potentially powerful tools for getting themselves re-elected. Presidents of either political party may therefore be tempted to arrange wars while waving the flag and calling the wars something else — “armed incursions,” “protective reaction strikes,” “pacification,” “safeguarding American interests,” and a wide variety of “operations”.

Sagan ends the chapter with a necessary disclaimer:

“Like all tools, the baloney detection kit can be misused, applied out of context, or even employed as a rote alternative to thinking. But applied judiciously, it can make all the difference in the world — not least in evaluating our own arguments before we present them to others.”