The Demon-Haunted World_ Science as a Candle in the Dark - Carl Sagan [102]
• 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,