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Knowledge, ignorance and climate change

Philosophers have been talking about scepticism for a long time. Some of those insights can shed light on our public discourse regarding climate change.

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According to Nasa, at least 97 per cent of actively publishing climate scientists think that climate-warming trends over the past century are extremely likely caused by human activities.

NO matter how smart or educated you are, what you do not know far surpasses anything that you may know. Socrates taught us the virtue of recognising our limitations. Wisdom, he said, requires possessing a type of humility manifested in an awareness of one's own ignorance.

Since then, the value of being aware of our ignorance has been a recurring theme in Western thought: Rene Descartes said that it is necessary to doubt all things to build a solid foundation for science; and Ludwig Wittgenstein, reflecting on the limits of language, said that "the difficulty in philosophy is to say no more than we know".

Awareness of ignorance appears to be common in politics as well. In a recent 60 Minutes interview, US President Donald Trump said of global warming, "I don't know that it's man-made." The same sentiment was echoed by Larry Kudlow, the director of the National Economic Council. Perhaps Mr Trump and Mr Kudlow, confident in their ignorance on these important issues, are simply expressing philosophical humility and wisdom. Or perhaps not.

Sometimes, when it appears that someone is expressing doubt, what he is really doing is recommending a course of action. For example, if I tell you that I do not know whether there is milk in the fridge, I am not exhibiting philosophical wisdom - I am simply recommending that you check the fridge before you go shopping. From this perspective, what Mr Trump is doing is telling us that governmental decisions should not assume that global warming is caused by humans.

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According to the National Aeronautics and Space Administration (Nasa), at least 97 per cent of actively publishing climate scientists think that "climate-warming trends over the past century are extremely likely caused by human activities".

Americans overwhelmingly agree that the federal government needs to take significant action. In a recent poll conducted by Stanford University, ABC News and Resources for the Future, 61 per cent of those surveyed said that the federal government should take a great deal or a lot of action to curb global warming. And an additional 19 per cent believe that the government should take moderate action.

As a philosopher, I have nothing to add to the scientific evidence of global warming, but I can tell you how it is possible to get ourselves to sincerely doubt things, despite abundant evidence to the contrary. I also have suggestions about how to fix this.

To understand how it is possible to doubt something despite evidence to the contrary, try some thought experiments. Suppose you observe a shopper at the convenience store buying a lottery ticket. You are aware that the probability that he will lose the lottery is astronomically high, typically above 99.99 per cent, but it is hard to get yourself to sincerely say that you know this person will lose the lottery.

Now imagine your doctor screens you for a disease, and the test comes out negative. But consider the possibility that this result is one of those rare "false negative" cases. Do you really know the result of this particular test is not a false negative?

These scenarios suggest that it is possible to feel as though you do not know something even when possessing enormous evidence in its favour. Philosophers call scenarios like these "sceptical pressure" cases, and they arise in mundane, boring cases that have nothing to do with politics or what one wants to be true.

In general, a sceptical pressure case is a thought experiment in which the protagonist has good evidence for something that he or she believes, but the reader is reminded that the protagonist could have made a mistake. If the story is set up in the right way, the reader will be tempted to think that the protagonist's belief is not genuine knowledge.

When presented with these thought experiments, some philosophy students conclude that what these examples show is that knowledge requires full-blown certainty. In these sceptical pressure cases, the evidence is overwhelming, but not 100 per cent. It is an attractive idea, but it does not sit well with the fact that we ordinarily say that we know lots of things with much lower probability.

For example, I know I will be grading student papers this weekend. Although the chance of this happening is high, it is not anything close to 100, since there is always the chance that I will get sick, or that something more important will come up. In fact, the chance of getting sick and not grading is much higher than the chance of winning the lottery. So how could it be that I know I will be grading and not know that the shopper at the convenience store will lose the lottery?

Philosophers have been studying sceptical pressure intensely for the past 50 years. Although there is no consensus about how it arises, a promising idea defended by the philosopher David Lewis is that sceptical pressure cases often involve focusing on the possibility of error. Once we start worrying and ruminating about this possibility, no matter how far-fetched, something in our brains causes us to doubt. The philosopher Jennifer Nagel aptly calls this type of effect "epistemic anxiety".

In my own work, I have speculated that an extreme version of this phenomenon is operative in obsessive compulsive disorder (OCD) - a condition that affects millions of Americans. In many cases of OCD, patients are paralysed with doubt about some fact - against all evidence. For example, a patient might doubt whether she turned off her stove despite having just checked multiple times. As with sceptical pressure cases, the focus on the possibility that one might be wrong plays a central role in the phenomenon.

Let's return to climate change scepticism. According to social psychology, climate change deniers tend to espouse conservative views, which suggests that party ideology is partly responsible for these attitudes. I think that we should also think about the philosophical nature of sceptical reactions, an apolitical phenomenon.

The standard response by climate sceptics is a lot like our reaction to sceptical pressure cases. Climate sceptics understand that 97 per cent of scientists disagree with them, but they focus on the very tiny fraction of holdouts. As in the lottery case, this focus might be enough to sustain their scepticism. We have seen this pattern before. Anti-vaccine proponents, for example, aware that medical professionals disagree with their position, focus on any bit of fringe research that might say otherwise.

Sceptical allure can be gripping. Piling on more evidence does not typically shake you out of it, just as making it even more probable that you will lose the lottery does not all of a sudden make you feel like you know that your ticket is a loser.

One way to counter the effects of scepticism is to stop talking about "knowledge" and switch to talking about probabilities. Instead of saying that you do not know some claim, try to estimate the probability that it is true.

As hedge fund managers, economists, policy researchers, doctors and bookmakers have long been aware, the way to make decisions while managing risk is through probabilities. Once we switch to this perspective, claims to "not know" - like those made by Mr Trump - lose their force, and we are pushed to think more carefully about the existing data and engage in cost-benefit analyses.

Interestingly, people in the grips of scepticism are often still willing to accept the objective probabilities. Think about the lottery case again. Although you find it hard to say that you know that the shopper will lose the lottery, you readily agree that it is still very probable that he will lose.

What this suggests is that even climate sceptics could budge on their esteemed likelihood of climate change without renouncing their initial scepticism. It is easy to say that you do not know, but it is harder to commit to an actual low probability estimate in the face of overwhelming contrary evidence.

Socrates was correct that awareness of one's ignorance is virtuous, but philosophers have subsequently uncovered many pitfalls associated with claims of ignorance. An appreciation of these issues can help elevate public discourse on important topics, including the future of our planet. NYTIMES

  • The writer is a professor of philosophy in the School of Historical, Philosophical and Religious Studies at Arizona State University