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Merchants of Doubt by Naomi Oreskes and Erik M. Conway.
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“Merchants of doubt” (MODs) are people or organizations who create the impression that scientific findings that threaten their agenda or ideology are unsettled or flat-out wrong. The goal is to stave off regulation to keep the economy free.

The tobacco industry pioneered techniques for manufacturing doubt when scientists discovered that smoking caused cancer, and other MODs had been attacking science using the same techniques ever since.

What Is Science?

Most of us don’t really understand what science is. We think it’s iron-clad proof that something is true. In reality, scientific knowledge is expert consensus—a group of qualified scientists agrees that a claim is correct when there’s enough evidence to support it.

Peer Review

Expert consensus comes from peer review. No science is considered legitimate until it passes peer review. Typically, the process works like this:

Step #1: A scientist comes up with an idea, collects evidence to support it, writes a paper, and then submits it to a scientific journal for publication.

Step #2: The journal sends the paper to three other scientists to review. Reviewers must be subject matter experts and mustn’t have a close relationship with the paper’s author. They look for bad science and mistakes and provide comments. If the reviewers provide conflicting comments, the journal might send the paper to more scientists or the editor might provide notes.

Step #3: The journal sends the reviewers’ notes back to the paper’s author to address. The author may write multiple drafts as she implements and receives new feedback. If the author ultimately fails to revise well enough, the journal won’t publish the paper. The author has to start over or try a different (less prestigious) journal.

How Does Uncertainty Work?

Even after a paper has passed peer review and been published, there will always be some uncertainty regarding the details—science is always evolving, so while we may know a lot, we’re never going to know everything about any topic. This is normal and important—it’s what drives scientists to keep discovering new things.

  • For example, climate modelers can’t effectively capture hurricanes because they’re too small (on a global scale).

When presented with an uncertainty, the question shouldn’t be whether there’s any doubt, but whether there’s any reasonable doubt. If there’s reasonable doubt, the matter isn’t settled. If there’s doubt on the details, that’s normal.

Who Are the Merchants of Doubt?

By nature, science challenges the status quo and ruling class because its purpose is to change our understanding of the world around us. Science often reveals market failures and suggests regulation as a solution, so merchants of doubt tend to be defenders of the free market such as:

  • Free market fundamentalists who believe that free markets are the only economic system that allows for freedom
  • Cornucopians or technophiles, who believe that technology will fix every one of humanity’s problems as long as markets stay free (so inventors will be motivated to innovate by huge rewards)

Four notable individual merchants of doubt—Fred Seitz, William Nierenberg, Robert Jastrow, and Fred Singer—were involved in doubt-mongering multiple scientific questions from the 1960s-2000s. All of them were media-savvy, well-connected, politically powerful, fiercely anti-Communist physicists (though none of them did much original science after 1970—they wrote reviews or editorials, but didn’t publish much in peer-reviewed journals).

Doubt-Mongering Techniques

There are 10 techniques that the merchants of doubt use to create debate around issues that are scientifically settled. This appearance of debate can influence public opinion and delay or even halt regulation.

Technique #1: Emphasize Uncertainty

MODs play up the natural uncertainty inherent in science to suggest that everything is uncertain.

Example #1: When scientists were studying the possible effects of a nuclear weapons exchange, the science was all based on projections because the only way to get evidence would have been to start a nuclear war and observe what happened. MODs claimed there was too much uncertainty around the possible consequences of an exchange to justify exposing the country to the dangers of disarmament.

Example #2: After scientists discovered that smoking caused cancer, there were still uncertainties, such as how exactly smoking causes cancer and why not all smokers get lung cancer (this is still unknown today). MODs tried to exaggerate these uncertainties into uncertainty about the whole question of whether smoking caused cancer.

Technique #2: Cherry-Pick Data

MODs only cite or publicize data that support their position, and they ignore anything that doesn’t.

For example, in 1989, the Marshall Institute (run by Jastrow, Nierenberg, and Seitz) put out a report that claimed the steady increase in atmospheric carbon dioxide couldn’t be responsible for global warming because the Earth’s surface temperature hadn’t steadily increased—there was warming before 1940 (before significant emissions), cooling from 1940-1975, and then more warming.

To support this, the report included a diagram that plotted CO2 against temperature. The lines didn’t match up particularly well, but that was because the MODs had only included part of the diagram. The full...

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Merchants of Doubt Summary Introduction

“Merchants of doubt” (MODs) are people or organizations who create the impression that scientific findings that threaten their agenda or ideology are unsettled or flat-out wrong. The goal is to stave off regulation.

The tobacco industry pioneered techniques for manufacturing doubt when scientists discovered that smoking caused cancer, and other MODs had been attacking science using the same techniques ever since.

In this book, science historians Naomi Oreskes and Erik M. Conway cover how science and doubt-mongering work, and they look at doubt-mongering campaigns around the following scientific questions:

  • Are tobacco and secondhand smoke a health hazard?
  • Would a nuclear defense system actually work, and would a nuclear war make the planet inhospitable?
  • Is acid rain real, and will it damage the environment?
  • Is the ozone hole real, and will it endanger humans?
  • Is climate change real, and can we do anything about it?
  • Is the pesticide DDT dangerous to the environment or humans?

Finally, they offer tips for evaluating whether information is doubt-mongering or real science.

(Merchants of Doubt was originally published in 2010 and then updated in...

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Merchants of Doubt Summary Chapter 1: Sowing Doubt

Now that we know how science, uncertainty, and cause work (and we know that a lot of people don’t understand how they work), we can look at how merchants of doubt exploit this to cause widespread public confusion.

Who Are the Merchants of Doubt?

By nature, science challenges the status quo and ruling class because its purpose is to change our understanding of the world around us. Science often reveals market failures and suggests regulation as a solution, so merchants of doubt tend to be defenders of the free market such as:

MOD Type #1: Free market fundamentalists, who believe that free markets are the only economic system that allows for freedom. These MODs are opposed to regulation, particularly international treaties because global governance reduces an individual nation’s powers.

However, free market fundamentalism is unsound—there are plenty of examples of market failure throughout history, such as the Great Depression. **Free market fundamentalism is particularly fallible in the case of the environment because it produces “negative externalities,” which are consequences and costs that aren’t reflected in the market system, so the market has no...

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Shortform Exercise: Reflect on Doubt-Mongering Techniques

Doubt-mongering techniques are powerful and widespread, and like everyone, you’ve likely been subjected to some of them.


Think of a time when you thought a scientific question about health or the environment was unresolved. What made you think there was uncertainty? Why?

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Merchants of Doubt Summary Chapter 2: Tobacco

In this chapter and the next, we’ll look at doubt-mongering around the science of tobacco use. The tobacco industry pioneered the manufacture of doubt with the help of Fred Seitz, and many of the techniques they came up with (and the people who implemented them) were used by future merchants of doubt. The doubt-mongering was so successful that it took over 50 years for the majority of the public to believe that smoking was dangerous to health.

Discovery of the Problem

Scientists have known that smoking is bad for you since the 1930s when German scientists discovered that smoking cigarettes caused lung cancer. (Lung cancer was uncommon before smoking became widespread.) However, because German science had Nazi associations, most people ignored it.

In the 1950s, scientists at the Sloan-Kettering Institute rediscovered the cancer-causing effects of tobacco when they painted cigarette tar on mice and the mice developed terminal cancer. Their research was widely publicized, striking fear in the hearts of those involved with the tobacco industry.

The MOD's Response

**The tobacco industry responded to the Sloan-Kettering Institute discovery by hiring PR firms to...

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Merchants of Doubt Summary Chapter 3: Secondhand Smoke

In the previous chapter, we looked at doubt-mongering around active smoking. Now, we’ll look at the doubt-mongering surrounding secondhand smoke (also called passive smoke or environmental tobacco smoke). Fred Singer helped the industry respond by again challenging the science. This time, though, the merchants of doubt didn’t just highlight uncertainty—they attacked the Environmental Protection Agency (EPA) for doing “bad science.”

Discovery of the Problem

In the 1970s, tobacco industry scientists discovered that secondhand smoke could cause cancer. In fact, they discovered that secondhand smoke was actually more toxic than active smoke. This was partly because more toxic compounds develop when cigarettes burn at a lower temperature (smoldering) than at a higher temperature (while smoking).

The industry responded to this discovery by:

  1. Attempting to make secondhand smoke less dangerous by making cigarettes smolder at higher temperatures or improving cigarette components such as filters or papers
  2. Attempting to make secondhand smoke less visible

Mainstream science started to unearth the health problems associated with secondhand smoke in the 1980s:

  • ...

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Merchants of Doubt Summary Chapter 4: Strategic Defense—Star Wars

In the last two chapters, we looked at how the tobacco industry pioneered and refined doubt-mongering around active and passive smoking. In this chapter and the next, we’ll look at doubt-mongering in another context: strategic defense and nuclear winter.

Unlike tobacco, where there was a lot of evidence that it caused health problems, the science around strategic defense and nuclear winter was all projection (the only way to get evidence would be to start a nuclear war).

The 1975 CIA National Intelligence Estimate

In 1975, the CIA and other U.S. intelligence agencies published a National Intelligence Estimate (NIE) that concluded that the U.S. was stronger than the Soviets in three key areas:

  1. Intercontinental ballistic missiles (ICBMs). The CIA thought that the Soviet ICBMs weren’t very accurate, so if the Soviets fired first, their missile would miss most of the U.S., leaving enough weaponry undamaged to retaliate.
  2. Air defense system. The CIA didn’t think the Soviet defense system could keep out low-flying U.S. bombers.
  3. Submarine location. The CIA believed that the Soviets couldn’t locate or defend against U.S. submarines. They also...

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Merchants of Doubt Summary Chapter 5: Nuclear Winter

In the last chapter, we looked at the science and doubt-mongering around strategic defense. Now, we’ll look at a related issue that also inspired research and doubt-mongering: nuclear winter.

Discovery of the Problem

During Reagan’s term, astrophysicists at NASA Ames Research Center were working with computer models to assess the effects that dust in the atmosphere has on the surface of planets. Initially, they were trying to learn about Mars’s atmosphere, but then they realized the models could help them figure out what had happened to the dinosaurs and what might happen after a nuclear war.

After something massive collides with the Earth, whether an asteroid or a nuclear warhead, fires start and huge amounts of dust fly into the atmosphere. Smoke and dust block the sun. Without the sun, the surface temperature cools and plants, unable to photosynthesize, die.

The models suggested that even a small nuclear exchange would create enough dust to lower the Earth’s surface temperature below freezing even in the summer. The drop would be 35 degrees Celsius. This would come to pass even if the exchange was small (somewhere between 500-2,000 warheads). Each superpower...

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Merchants of Doubt Summary Chapter 6: Acid Rain

In the previous chapters, we looked at doubt-mongering surrounding public health and national security issues. From here, we’ll look at doubt-mongering related to the environment. Environmental issues are thorny because:

1. They often expose market failure. Markets don’t self-regulate when it comes to pollution or environmental damage because their effects don’t contribute to the cost of a service or good. (See Chapter 1 for more details.) When markets fail, governments often intervene.

Therefore, environmental issues are major targets for MODs, who support free-market economics and abhor government interference.

There are three major ways the government intervenes:

  • Cap-and-trade. The government sells a limited number of permits to pollute, and companies can buy or trade them. This makes pollution part of the free market system.
  • Direct R&D funding. The government funds programs that will reduce pollution and environmental damage.
  • Regulation. The government legislates how much companies can pollute. Researchers at Carnegie Mellon found that regulation is likely the most effective intervention because it encourages innovation—companies have to...

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Merchants of Doubt Summary Chapter 7: Ozone Hole

In the last chapter, we looked at the “debate” over acid rain, which the merchants of doubt successfully fueled. In this chapter, we’ll look at the “debate” over the ozone hole, which didn’t fall prey to doubt-mongering.

Discovery of the Problem

The discovery of the ozone hole was roundabout—scientists found it while studying something else.

Supersonic Transports (SSTs)

In the late 1960s, the U.S. wanted to build supersonic transports (SSTs), commercial planes that could break the sound barrier. Unlike regular planes, the SST would travel in the stratosphere, and scientists were concerned the plane’s exhaust (composed of carbon dioxide, water vapor, and nitrogen oxides (NOX)) might damage the environment because:

  • Carbon dioxide and water vapor are greenhouse gases. (See Chapter 8 for more on the greenhouse effect and climate change.)
  • Water vapor contributes to cloud formation, which can change the weather.
  • Water vapor and NOX might deplete the stratospheric ozone layer. By the 1970s, scientists knew that the ozone layer blocked the sun’s UV radiation, which could cause some types of skin cancer.

**In 1970, two notable studies tackled the...

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Merchants of Doubt Summary Chapter 8: Climate Change

In the last chapter, we looked at an example of science successfully informing policy despite the interference of the merchants of doubt. Now, we’ll look at the opposite case—the MODs discrediting science enough to stop policy on one of the more important issues of the day: global warming and climate change. Climate change is a hugely inflammatory issue for the MODs because addressing it would involve regulating energy use, which is the keystone of economic activity.

Discovery of the Problem

Research on atmospheric carbon dioxide (CO2) and its effect on climate started over 150 years ago:

  • In the mid-19th century, experimentalist John Tyndall discovered that CO2 in the air traps heat in the atmosphere.
  • In the early 20th century, geochemist Svante Arrhenius discovered that CO2 emissions from burning fossil fuels could change the planet’s climate. Engineer Guy Callender found evidence that CO2 might already be creating the “greenhouse effect” (the atmosphere acts like a greenhouse, letting heat in but not letting it out).
  • In the 1950s, chemist Charles David Keeling measured CO2 and found that it had been...

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Shortform Exercise: Reflect on Climate Change

The doubt-mongering campaign about climate change is still ongoing.


When and how did you first become aware of climate change?

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Merchants of Doubt Summary Chapter 9: DDT

In the previous chapters, we looked at how merchants of doubt created debate around emerging and unregulated issues to halt or at least delay government interference. In the case of the pesticide DDT, the MODs manufactured doubt when the issue first came up, but they also reprised their doubt-mongering years later, after the matter had been settled and DDT had been banned for years in the U.S.

The goal of the second DDT doubt-mongering campaign was to:

  • Convince people that past government regulation was a mistake. If banning DDT had caused harm, MODs could make the case that regulation was a bad idea in general.
  • Convince people that the shift in U.S. environmentalism from defending the beauty of nature to regulation was a mistake. Again, if regulating DDT was a mistake, then perhaps the whole shift had been a mistake.

They weren’t trying to get DDT unbanned—it wasn’t even an effective pesticide anymore—they were just trying to defend free-market forces.

Discovery of Problem #1: DDT Creates Resistance in Insects

The chemical DDT (dichlorodiphenyltrichloroethane) was first invented in 1873, but no one was particularly interested in it. When...

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Merchants of Doubt Summary Chapter 10: Fighting Doubt

In the previous chapters, we learned the techniques merchants of doubt use to manufacture doubt, and we looked at several examples of how they successfully employed them. The merchants of doubt continue their work today, and in this chapter, we’ll look at some of the issues they’re tackling and how to protect ourselves from being taken in.

Doubt-Mongering Today

The original edition of Merchants of Doubt was published in 2010 and updated in 2020. Despite the MOD’s victories in the climate change arenas pre-2010, Oreskes and Conway thought things might be improving because:

  • The media was decreasing its coverage of climate change deniers.
  • The 2006 documentary An Inconvenient Truth helped show Americans that anthropogenic climate change was very real.
  • In 2007, Al Gore’s work on climate change made him a shared winner of the Nobel Peace Prize.
  • The Obama administration was making progress against the fossil fuel industry and Republicans.
  • Most importantly, a coalition of territories, cities, and groups led by Massachusetts sued the Environmental Protection Agency (EPA) for failure to adhere to the Clean Air Act—the act requires the government to...

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Shortform Exercise: Identify Doubt-Mongering and Expert Consensus

Doubt-mongering is a powerful tool, but since it doesn’t have science (expert consensus) on its side, it is possible to see through it.


Think of a contentious scientific question that has the potential to change policy. (For example, you might consider plastic pollution.) Who supports policy changes and who opposes them?

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