Humans have an evolutionarily rooted propensity to classify situations as simply 'safe' or 'unsafe' (an on/off 'danger sign'), which is unhelpful for good decision-making because real risks come in gradations rather than as a binary switch.

There is no such thing as a truly 'safe' drug, treatment, surgery, or device; for both individuals and the FDA there are only gradations of risk, and when stakes are high one should evaluate both the magnitude of the danger and its probability rather than relying on a safe/unsafe label.

People (including trained statisticians and law students) struggle to reason differently about a 10% probability versus a 30% probability of harm, because the mind does not naturally treat probabilities along a continuum, especially after an event has occurred or when reasoning anticipatorily about personal stakes.

When probabilities cannot be assigned with confidence (a wide band of uncertainty), the standard expected-value approach of multiplying outcomes by probabilities breaks down, so decision-makers may need simplifying rules of thumb instead.

Cheney's '1% doctrine'—treating a 1% chance of a catastrophe like a nuclear terrorist attack as if it were a near-certainty—is flawed because, even in the domain of catastrophe, a 1% chance is fundamentally different from a 100% chance and should not be treated identically.

Aggressive responses to catastrophic risks themselves impose costs and create new risks: aggressive greenhouse-gas regulation produces certain adverse effects (higher energy prices harming the poor) and a remote but nonzero risk of international instability from economic distress, while anti-terrorism responses create civil-liberties risks and can increase other terrorist risks.

The differing American reactions to terrorism (hundreds of billions spent post-9/11) and climate change (similar costs viewed as unaffordable) can be partly explained as rational self-interested cost-benefit analysis: climate remedies were perceived to mostly benefit foreigners in the distant future at high domestic cost, while terrorism precautions were seen as cheap relative to high perceived domestic benefits.

A single salient event (like 9/11) can have a massive, possibly disproportionate effect on intuitive cost-benefit analysis of worst-case scenarios; terrorism had such an event while climate change lacked one (Hurricane Katrina failed to serve as climate's 9/11), and this difference largely explains the asymmetric policy responses.

When an emotionally gripping outcome is at stake, people exhibit 'probability neglect'—they focus on how terrible the outcome would be while ignoring its likelihood; terrorist attacks have this emotional grip while gradual, hard-to-visualize climate change does not.

Outrage—particularly the presence of an identifiable human face responsible for a risk—is a powerful magnifier of attention to worst-case scenarios; terrorism has a face (Osama bin Laden/Al Qaeda) that magnifies concern, while climate change has no villainous face and is therefore diminished in salience.

Even several years after 9/11, Americans across the country estimated something like a 20-30% probability that they or someone they knew would be killed in a terrorist attack within the next year—a wildly inflated personal threat assessment that is hard to justify on available information, undermining the 'rational updating' explanation.

After 9/11, almost as many people died from foregoing air travel in favor of driving as would be expected, because statistical analysis even shortly after 9/11 showed driving was at least not safer than flying, yet people remained scared of flying while comfortable driving.

The availability heuristic causes people to assess probabilities not like statisticians but by how easily they can recall an example; this explains why people wrongly believe homicides exceed suicides and accidents exceed diseases as causes of death, when the reverse is true, because homicides and accidents are more salient/available.

A feeling of personal control (such as being at the wheel while driving) can diminish perceived risk even when statistically unjustified, which partly explains why people fear flying more than driving.

Driving more rather than flying can now be a rational choice because of the added time costs and inconvenience of flying (security lines), even if driving is statistically more dangerous.

The U.S. under Reagan aggressively attacked ozone depletion and was more aggressive than Europe, with Washington Republicans pushing for action, because the Council of Economic Advisers showed that phasing out ozone-depleting chemicals was a tremendous bargain (~$21 billion cost) yielding far larger benefits in reduced cataracts and skin cancer—even unilateral U.S. action would have been justified.

The Kyoto Protocol was rejected on a bipartisan basis (the Senate voted 95-0 against, no Democratic senator supported ratification) because it would have cost the U.S. upwards of $300+ billion (bearing 50-80% of worldwide costs) while delivering near-zero monetized U.S. benefits—since the developing world was excluded and the existing stock of greenhouse gases unaffected—reducing anticipated 2100 warming by only about 0.03°C.

U.S. cities and states (notably California) adopting costly emissions reductions that deliver essentially no climate benefit is explained by a combination of confusion (not seeing that the problem requires broad international participation), hope (that local action may trigger a cascade spurring international action), and a perceived moral obligation toward vulnerable nations like India and African countries that face severe harm even from moderate (~2.5°C) warming.

Collective-action problems lead people to believe their own small contribution will matter or spur others even when it will not, which underlies confused individual and subnational efforts on climate change.

Some social risks are exploited by self-interested 'bootleggers and Baptists' coalitions where politicians look green or protective while funneling resources to favored special interests—e.g., the corn lobby benefiting from ethanol policies, or European farmers manufacturing GMO-food fears as a protectionist tool to scare consumers away from American products.

'Worst-case entrepreneurs' fan the flames of fear by exploiting public ignorance and making low-probability risks more salient; they attacked nuclear power successfully by invoking Three Mile Island (which was not actually a disaster) and Chernobyl, giving nuclear power an undeserved 'bum rap' that has harmed U.S. energy development.

Imposing large costs on the private sector causes deaths because people become poorer and less employed; data suggest roughly a $7 million expenditure causes at least one statistical death, so a $40 million regulatory expenditure (not unusual) probabilistically causes five or six or more deaths, which itself violates the precautionary principle.

Worst-case entrepreneurs invoking the risks of DDT (e.g., via Rachel Carson's Silent Spring) helped drive an international consensus to ban it, which—while justified in the U.S.—created a worse-case scenario of its own in the developing world, where DDT is the most effective and cheapest way to prevent malaria, leading to large numbers of human deaths; risks frequently exist on both sides of social situations.

The political process acts as an aggregator of individual preferences, and politicians respond to voter voices, so the U.S. banned ozone-depleting chemicals (a good deal for Americans) but stayed indifferent to costly global-warming action—whereas in poor countries ruled by tyranny the voice of the people matters far less, possibly explaining differential international responses to risks like DDT bans.

Once a country becomes dependent on a technology like nuclear power, it is very hard to reverse course, as in France, where an early decision with a powerful trusted government and little intense opposition entrenched nuclear power—analogous to Finland's unresponsiveness to cell-phone/cancer fears because Nokia and cell-phone use are central to its economy.

The precautionary principle in its strong versions (placing the burden on a proponent to prove an activity is safe) is incoherent and paralyzing because it forbids the very steps it requires: banning nuclear power on precautionary grounds itself creates probabilistic risks (including climate change), so the principle simultaneously compels and prohibits action, inaction, and everything in between.

The tendency to respond to a salient tragedy by removing its cause—such as requiring baseball coaches to wear helmets after a one-in-a-million freak fatality, or laws and precautions during the shark-attack scare—is a remarkable human phenomenon that is usually hard to justify on all-things-considered grounds, especially given possible unintended consequences like reduced caution from a false sense of safety.

Government risk regulation legitimately differs from individual decision-making: because governments operate population-wide, they can reasonably worry about one-in-a-hundred-thousand risks or less, whereas for most individuals most of the time such precautions make no sense because the associated anxiety is itself a cost (and an adverse health effect) that exceeds the precaution's benefit.

Testing for a rare disease with an imperfect test can be harmful: a 95%-accurate test for a condition with one-in-a-thousand prevalence (e.g., lupus) yields only about a 2% chance of actually having the disease given a positive result, so when no treatment exists, such testing mainly creates false alarm and is a disastrous thing to do.

Because human history suggests the future will be much richer than the present, it makes no sense for the relatively impoverished present to transfer resources to the far wealthier future; sacrificing economic growth now also hurts the future because long-term growth produces citizens who live healthier, longer, and better lives.

Mammals generally operate in a binary fight-or-rest mode—'I can go to sleep or I have to stay awake'—which mirrors the human safe/unsafe instinct.

One must separate two distinct ideas: 'intergenerational neutrality'—that a life 100 years from now is worth no less than a life today, so we should be equally concerned about future and present people—from the discounting of money, where a dollar today is genuinely worth more than a dollar in 2100; failing to discount money while honoring life-neutrality could itself harm future people by impoverishing the present and forgoing prosperity that yields human goods.

The right way to handle intergenerational tradeoffs is to ask what future generations would want: sometimes they would want us to take precautions, but often they would say 'grow, and we will come up with ways to cope,' since being wealthier enables coping—so we should neither control all pollution nor none of it.

Irreversibility is where concern for future generations genuinely bites: irreversible losses (e.g., the Grand Canyon or a starlit sky) that deprive future generations of options with no good substitutes warrant special weight—but an irreversible loss should not be treated as infinitely valuable, and many feared harms (like skin cancer) will likely be cured within a century.

We already transfer enormous resources into the future—not merely through bequests but through the immense time and effort spent on our children and loved ones—a fact often ignored in discounting debates.

Entrepreneurs who claim they only need '1% of the market' or '1% of the book market' frame it as a cautious goal, but achieving even 1% of a large market is actually a remarkably ambitious claim.