There are two basic kinds of reasoning; deduction and induction. Deduction consists of putting together statements about generalizations, or categories, and then drawing a specific conclusion from those statements. Induction is, in a way, the opposite; analyzing specific instances of phenomena, and then inferring a general, overarching pattern from them.
Neither is infallible. Deductive logic, for example, is only as good as the premises. The argument, "All dogs have tails; boxers do not have tails; therefore boxers are not dogs" is a perfectly valid piece of deduction (it follows the pattern called modus tollens), but it leads to a wrong conclusion because it started out with a false premise (that all dogs have tails). In induction, it is the process of inference that can lead you astray; there might be instances you haven't considered, causalities about which you were unaware. No one was more aware of this than Einstein -- when congratulated on experimental data having proven his Special Theory of Relativity, Einstein soberly replied, "A thousand experiments could not prove me right, but one could prove me wrong."
However, there is a vast public misperception that both of these methods of reasoning are (or should be) infallible. Logic, of either flavor, should always lead you to correct answers. More to the point, if scientists know what they are doing, they should be able to get it right every single time. If they don't get it right, something serious is amiss -- perhaps they have a political agenda that they are trying to foist. Maybe they fudged their data to get grant money.
Or maybe they're just criminally malfeasant.
That last one is the chilling conclusion reached in Italy Monday regarding six geologists, who the courts declared guilty of manslaughter because of their failure to predict the earthquake in L'Aquila in 2009 that killed over 300 people. The judge sentenced each of them to six years in prison, and the government agency for which they worked (the National Institute of Geophysics and Volcanology) to pay 7.8 million euros ($10 million) in damages. [Source]
This is such a bizarre miscarriage of justice that I barely know where to begin.
Saying "scientists are human, and therefore fallible" is only the shallowest layer of why this verdict is absurd. It's more than just six fallible individuals who made a regrettable mistake; it's a complete misunderstanding of what science and inductive reasoning does, and in fact what it is capable of doing. Scientific inference is never going to give you certainty; even in fields about which a great deal is known, and about which the mechanisms are generally understood (let's say, biological evolution), there will always be pieces of the puzzle that don't seem to fit. There are still species (plenty of them) whose position on the Grand Tree of Life is poorly understood, and therefore subject to revision; there will always be features, adaptations, and structures still to explain. If they weren't, well, we biologists would be out of a job, wouldn't we? There'd be nothing left to research.
The necessity of maintaining an awareness of uncertainty, of living on the edge of what is known, is even more pronounced when you are in a realm of science about which the mechanisms are only partly understood. Climatology falls into this category -- and so does seismology. While we understand a great deal more about these subjects than we did fifty, or even twenty, years ago, they are not yet at the point of being models that can predict with anything near 100% accuracy. (And as I pointed out above, 100% isn't reachable no matter what.)
The fact that scientists in general, and especially ones in fields that are perched on the edge of what is explainable, get it wrong sometimes is inevitable. More importantly, these missteps aren't indicators of some hidden agenda, or of outright malfeasance; they are indicators that we don't fully understand the system being studied. Which we already knew, right? The fact that climatologists are nearly unanimous in attributing the climate changes we've seen in the past century to anthropogenic carbon dioxide doesn't mean that they can yet tell you how those changes will manifest in weather events day after tomorrow, or how far those trends will continue, or what the ultimate result will be for the Earth's climate. The fact that seismologists understand a great deal about plate tectonics doesn't mean that they can tell you when and where the next major earthquake will strike. We simply don't have enough information yet to make those kinds of pinpoint-accuracy predictions.
I trust science. I trust the majority of scientists. At the same time, I am always aware of its limitations and boundaries, and the fact that by nature, inductive reasoning gives you a tentative, incomplete picture of the world. "Scientists are always at the drawing board," astronomer Neil DeGrasse Tyson said. "If they're not at the drawing board, they're not doing science. They're doing something else." The six scientists who are facing prison terms in Italy are where they are because inevitably, the scientific process generates partial solutions and uncertain predictions. That's simply how science works. Progress is made in science not by someone having a flash of insight and figuring out the "right answer," but by slow, painstaking motion toward a model that seems to be consistent with everything that is observed, the majority of the time.
To put it bluntly, the judge who ruled them guilty of manslaughter apparently has no understanding whatsoever of science as a process. My fear is that this verdict will place a further chill on scientific research -- a scary thought, in a time when accusations of political bias, and claims that pure research is a waste of money, are already chipping away at the public's perception of science as a worthy endeavor. Who will want to publish a supported, but controversial, result if now you not only can be accused of having a secret agenda, or wasting money, but be found criminally responsible if your model turns out to be wrong, if your predicted results don't come to pass? In one way, saying "scientists are only human" is relevant -- scientists have lives, and families, and value their freedom, and if they think that some idiot judge is going to imprison them for manslaughter because they failed to predict an earthquake, they are likely to leave the field altogether. Which, incidentally, two other Italian seismologists, Mauro Dolce and Luciano Maiani, did on Tuesday after hearing about the verdicts.
The whole thing is a travesty of justice. I don't know enough about the Italian judicial system to know with any certainty how likely it is that an appeal will be successful, but it is to be hoped that these men will ultimately be freed and their names cleared of these charges. If not, I fear for the future of science, which remains our best and most reliable method for finding out about the world we live in.