• Quantify. 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 truths to be sought in the many qualitative issues we are obliged to confront, but finding them is more challenging.
• If there’s a chain of argument, every link in the chain must work (including the premise) – not just most of them.
• Occam’s Razor. This convenient rule-of-thumb urges us when faced with two hypotheses that explain the data equally well to choose the simpler.
• Always ask whether the hypothesis can be, at least in principle, falsified. 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. But if we can never acquire information from outside our Universe, is not the idea incapable of disproof? You must be able to check assertions out. Inveterate sceptics must be given the chance to follow your reasoning, to duplicate your experiments and see if they get the same result.
The reliance on carefully designed and controlled experiments is key, as I tried to stress earlier. We will not learn much from mere contemplation. It is tempting to rest content with the first candidate explanation we can think of. One is much better than none. But what happens if we can invent several? How do we decide among them? We don’t. We let experiment do it. Francis Bacon provided a classic reason:
Argumentation cannot suffice for the discovery of new work, since the subtlety of Nature is greater many times than the subtlety of argument.
Control experiments are essential. If, for example, a new medicine is alleged to cure a disease 20 per cent of the time, we must make sure that a control population, taking a dummy sugar pill which as far as the subjects know might be the new drug, does not also experience spontaneous remission of the disease 20 per cent of the time.
Variables must be separated. Suppose you’re seasick, and given both an acupressure bracelet and 50 milligrams of meclizine. You find the unpleasantness vanishes. What did it – the bracelet or the pill? You can tell only if you take the one without the other next time you’re seasick. Now imagine that you’re not so dedicated to science as to be willing to be seasick. Then you won’t separate the variables. You’ll take both remedies again. You’ve achieved the desired practical result; further knowledge, you might say, is not worth the discomfort of attaining it.
Often the experiment must be done ‘double-blind’, so that those hoping for a certain finding are not in the potentially compromising position of evaluating the results. In testing a new medicine, for example, you might want the physicians who determine which patients’ symptoms are relieved not to know which patients have been given the new drug. The knowledge might influence their decision, even if only unconsciously. Instead the list of those who experienced remission of symptoms can be compared with the list of those who got the new drug, each independently ascertained. Then you can determine what correlation exists. Or in conducting a police line-up or photo identification, the officer in charge should not know who the prime suspect is, so as not consciously or unconsciously to influence the witness.
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. Among these fallacies are:
• Ad hominem – 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).
• Argument from authority (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).
• Argument from adverse consequences (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).
[* A more cynical formulation by the Roman historian Polybius: Since the masses of the people are inconstant, full of unruly desires, passionate, and reckless of consequences, they must be filled with fears to keep them in order. The ancients did well, therefore, to invent gods, and the belief in punishment after death.]
• Appeal to ignorance – 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.
• Special pleading, often to rescue a proposition in deep rhetorical trouble (e.g., how can a merciful God condemn future generations to unending 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. Or: how could God permit the followers of Judaism, Christianity and Islam – each in their own way enjoined to heroic measures of loving kindness and compassion – to have perpetrated so much cruelty for so long? Special plead: you don’t understand Free Will again. And anyway, God moves in mysterious ways).
• Begging the question, 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?).
• Observational selection, also called the enumeration of favourable 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).
[* My favourite example is this story, told about the Italian physicist Enrico Fermi, newly arrived on American shores, enlisted in the Manhattan nuclear weapons project, and brought face-to-face in the midst of World War Two with US flag officers:
So-and-so is a great general, he was told.
‘What is the definition of a great general?’ Fermi characteristically asked.
‘I guess it’s a general who’s won many consecutive battles.’
‘How many?’
After some back and forth, they settled on five.
‘What fraction of American generals are great?’
After some more back and forth, they settled on a few per cent. 1 But imagine, Fermi rejoined, that there is no such thing as a great general, that all armies are equally matched, and that winning a battle is purely a matter of chance. Then the chance of winning one battle is one out of two, or 1/2; two battles 1/4, three 1/8, four 1/16, and five consecutive battles 1/32, which is about three per cent. You would expect a few per cent of American generals to win five consecutive battles, purely by chance. Now, has any of them won ten consecutive battles…?]
• Statistics of small numbers – a close relative of observational selection (e.g., ‘they say 1 out of 5 people is Chinese. How is this possible? I know hundreds of people, and none of them is Chinese. Yours truly.’ Or: V’ve thrown three sevens in a row. Tonight I can’t lose.’).
• Misunderstanding of the nature of statistics (e.g., President Dwight Eisenhower expressing astonishment and alarm on discovering that fully half of all Americans have below average intelligence).
• Inconsistency (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 in the major industrial nations) to the failures of capitalism. Or: consider it reasonable for the Universe to continue to exist forever into the future, but judge absurd the possibility that it has infinite duration into the past).