Despite the disturbing consequences, let’s consider whether a case can be made against the idea of active harm and passive harm being inherently different from a moral standpoint. Consider the following:

As in the Poe classic, a man is tied to a board, and above him a pendulum, with a sharp blade attached to it, swings back and forth. We will compare two scenarios. In both, imagine that you are standing near the man, and by some means are being monitored by a machine that operates the pendulum. In both cases, assume that you have complete information about the situation, and that there is no good reason that this man should die. Furthermore, assume that he has no hope of immediate escape (beyond what is stipulated in the scenarios) and that his death will involve enormous suffering.

Scenario 1.  (Passive Murder)

As the pendulum swings, it is slowly being lowered by the machine that operates it. If the pendulum gets low enough, the man will die. The machine monitors your motion. It has a rule programmed in it such that if your first movement is towards the man, the pendulum will be shut off. If, on the other hand, your first movement is away from the man, the machine will not react to your movement in any way (i.e. the pendulum will continue to be lowered and the man will die).

Scenario 2. (Active Murder)

As the pendulum swings, it stays at a fixed height (i.e. it is not being lowered toward the man). The machine monitors your motion such that if your first movement is away from the man, it will react by beginning to lower the pendulum (which will eventually kill the man). If, on the other hand, your first movement is towards the man, the machine will not react in any way (i.e. the pendulum will continue to remain at a fixed height, so the man will live).

Let’s compare these two scenarios. In Scenario 1, the man is already going to die unless you act by moving towards him. Hence, if you move away from him, you will be failing to help him, but you will not be actively killing him since the machine is already in the process of killing him and will not change its operation in any way if you move away. On the other hand, in Scenario 2, the man is not going to die unless you move away from him. Hence, if you move away from him you are actively killing him, since you are knowingly activating the machine, causing it to begin lowering the pendulum. Therefore, if failing to help a person is ethically superior to actively harming them, then moving away in Scenario 1 (where it has no effect) is ethically superior to moving away in Scenario 2 (where it causes the machine to initiate the death process).

At the same time we observe that despite this active versus passive distinction, the two scenarios are almost identical. In both cases, if you move towards the man he will not be killed, and if you move away from him he will be killed. In both cases it is trivially easy to perform either action. In both cases you have complete knowledge of the consequences of your actions. In both cases you are deciding whether he lives or dies. The only important difference between the scenarios is that in one, the machine happens to be lowering the pendulum already, whereas in the other it happens to be doing nothing. However, after you act (by moving towards the man or away from him) the resulting situation will be identical whether you are in Scenario 1 or Scenario 2.

If you believe that active harm is inherently better than passive harm, then you must therefore conclude that walking away in Scenario 1 is superior ethically to walking away in Scenario 2. Is this something you are truly willing to accept? In both cases walking away will mean the man will die, and preventing his death is equally easy in both cases. Can we really conclude that the initial motion of the pendulum is sufficient to change the ethical characteristics of the problem?

When it comes to belief about God, people often apply a different standard of evidence than they do to all other situations. Most everyone would be willing to say that “there is no rabbit living on the moon”, even though they cannot know this with certainty. After all, it is hypothetically possible that putting a rabbit on the moon was a part of some secret military project. And yet (despite their willingness to deny the moon rabbit), a great many people who find the existence of a God very improbable are not willing to say “there is no God” or even “I don’t believe in God.” This is likely, in part, due to cultural sensitivity (a claim that God does not exist certainly is offensive to some people) and it could also be related to the high stakes involved (if God is as he is perceived by many of the world religions, He has the power to punish and reward, so some may think it’s best not to take the risk of bad mouthing Him, even if you strongly doubt His existence). But it seems that another factor at play is the bizarre and essentially ridiculous redefining of the word “believe” that occurs in the God context.

While I have met a great many non-believers and self proclaimed atheists, I have never heard anyone claim that they could absolutely disprove the existence of all possible forms of God. In fact, using some definitions of “God” (such as an unspecified “higher power”) God cannot be disproven even in theory. Furthermore, an all powerful God, if He existed, could simply make us 100% certain in His absence while he continues to exist, showing that we can never eliminate ALL possibility of such a being.

I have again and again encountered people who, when asked whether they believe in God, claim they are agnostic (or won’t say outright that God doesn’t exist), but when asked how probable they think God is, say something to the effect of “highly improbable.” If it is reasonable to say that “rabbits on the moon do not exist” when such rabbits seem highly improbable, why shouldn’t a person say “God does not exist” if they feel God is equally improbable? The (now somewhat popular) notion that those who say they do not believe in God (or those who say they are atheists) think they can disprove Him with 100% certainty is not compatible with common English usage or with common sense.

First of all, since all headaches go away eventually, whether yours goes away or not isn’t really the relevant question. It would be better to ask how quickly the headache goes away. But even this question is not necessarily good enough, because even if aspirin doesn’t relieve a headache fully, a significant reduction in severity is still worthwhile.

In light of this, you may decide that when you next notice having a headache, you’ll make a record of how you feel every half hour for the next two hours. You’ll write things like “dull, throbbing pain of low intensity” or “sharp, searing pain over one eye”.

Unfortunately, just examining how you feel after taking aspirin a single time probably won’t be adequate, since the aspirin may be more helpful some times and less helpful other times. For example, perhaps it works on moderate headaches but not on really severe ones, so if your next headache happened to be really severe, it would look like aspirin was useless. To solve this problem and give yourself more data, you might resolve to make these records of how you’re feeling for each of the next 20 headaches you get.

There is still a problem though, because these subjective descriptions of headaches are difficult to compare to each other. It you take aspirin and your headache goes from a sharp pain over one eye to an intense ache over the entire head, have you made things better or worse? It would be difficult to aggregate the information from these varied descriptions over 20 different headaches to make a final assessment of how well aspirin is working.

Analysis would be a lot easier if you scored how unpleasant each headache was on a simple scale from 1 to 5 (1 meaning slight unpleasantness, 3, moderate unpleasantness, and 5, extreme unpleasantness). That way, you can simply look at all the scores you got just before taking aspirin and average them together. You can then compare this to the average of the scores 30 minutes after taking the aspirin and 60 minutes after taking it. That way, you can see if the amount of headache unpleasantness you feel really does drop substantially after taking aspirin.

You are interested in determining how effective aspirin is at relieving headaches, but all you’ve done so far is measure how good it is at relieving your own headaches. Perhaps you are more or less sensitive to aspirin than other people, or perhaps your headaches are more severe and harder to treat than most other people’s. To solve this problem, you enlist 20 people who are frequent headache sufferers. You get them to agree that, over the next 6 months, any time they begin to notice that they have a headache they will record how they feel on your 1 to 5 unpleasantness scale. They will then take aspirin and record how they feel again 30 and 60 minutes later.

But what if people take different doses? You might think that the aspirin isn’t working for some of them, but it’s only because they haven’t taken enough. To fix this problem, you hand them each an identical bottle of pills and tell them to take two whenever they get a headache (the maximum recommended dose). This also has the added benefit that everyone will be taking the same exact brand. That way if you find out that the aspirin really does work, other people can try to replicate your results by using the same brand that you did. On second thought, you also provide everyone with a timer that measures 30 minute intervals, to help them be more accurate about making records of their pain at almost exactly 30 and 60 minutes.

There is still a problem though. You know that headaches often become less severe within an hour or so even when you don’t take aspirin. That means that even if someone’s pain score tends to have fallen 60 minutes after taking the aspirin, you don’t really know whether it is the aspirin that caused the reduction in pain or if the reduction would have occurred regardless. To remedy this, you come up with the idea of having only half of the people take aspirin when they have a headache, though everyone will still keep a record of their headache’s progression. Then, to see how well the aspirin worked, you can compare the average 30 minute and 60 minute scores of the 10 people who took the aspirin each time with the scores of the 10 people who didn’t take any aspirin. If the aspirin group’s pain fell a lot more than the non-aspirin group, then the aspirin probably was the cause.

But is it possible that the pain levels people record could be influenced by the act of taking a pill, independent of the chemical effect of the active ingredients? For example, what if, because they expect the aspirin to work, the people in the group taking the pills are more aware of signs of improvement? In that case, the aspirin would seem to work better than it really does. Or perhaps people’s expectations of improving could even influence how much pain they experience. Fortunately, these problems are easily remedied. Instead of giving half the group no aspirin, you instead give them pills in an aspirin bottle that look just like aspirin, but which have no effect on headaches. Sugar pills are a reasonable choice, because pretty much everyone has sugar in their diet anyway, and small amounts of it (like the amount in two little pills) won’t have any noticeable effect on a person.

This raises ethical considerations, however. You got people to agree to take aspirin, not to take sugar pills. That means that beforehand you’ll need to inform everyone that they might be getting aspirin, but they also might be getting sugar pills instead. You can’t let them know which they are getting during the six months that they are recording their results, but afterwards, you can let them know which they were on. You’ll also have to get them to agree to not take any other headache medication during the experiment, and to record any medication that they do happen to take, or else it might throw off the results.

So half of your group will be taking aspirin, and the other half will get sugar pills. But who should get which? If, for example, the 10 people getting the aspirin have headaches that naturally (without treatment) last much longer than those of the 10 people that aren’t getting anything, then the aspirin may seem less effective than it really is.  Hence, you don’t want there to be any substantial difference between the two groups. A simple way to help ensure this is to assign individuals to the two groups (i.e. the aspirin group or the sugar pill group) at random. It is even better if someone else does the randomization (secretly recording which person is assigned to which type of pill). That way when you talk to the subjects about the experiment, there is no chance that you accidently tip them off  (with body language, or otherwise) to which type of pill they are getting. Furthermore, when you analyze the final results, you won’t have any temptation (subconscious or otherwise) to make the data come out a particular way (since you won’t know until you are done which subject was taking the aspirin and which was taking the sugar pill).

Unfortunately, if you carried out this experiment multiple times, you should expect to get slightly different results. After all, the people you would be able to recruit might be different and so might respond differently to the medicine. What’s more, even if you used the same people each time, the intensity of their headaches might vary from one 6 month period to the next, which could also influence how the results turn out.

But, if the results fluctuate randomly, that implies that sometimes, just by luck alone, the aspirin might seem to be effective even if it is not. Likewise, it might seem to be ineffective, even if it does work. So whatever it is that your experiment shows, how can you be sure you are really getting the right answer? Well, since chance is involved, total certainty is not possible. But a statistician could easily calculate for you the probability that you would get results (in favor of aspirin working) that are at least as strong as the ones that you got, if in fact aspirin is no more effective than the sugar pill. If this probability is large, then based on your experiment you do not have sufficient evidence to conclude that aspirin is an effective treatment for headaches. If this probability is small (say, less than 5%), then aspirin very likely is effective. In order to increase the likelihood that the results of your test are conclusive, you would need only to increase the number of participants involved.

Hence, we see that in order to answer questions with a high degree of certainty, a well thought out methodology is necessary. Most elements of good study design become obvious when we reflect logically on the ways that data may mislead us. Whenever possible, experiments should be double blind with a placebo control. They should have large sample sizes, standardized dosages, a standardized (and predetermined) method for outcome measurement, and careful statistical analysis. Without all of these in place, experiments simply cannot be trusted (for reasons that become obvious, with just a little thought).

Keep the faith, don’t lose your perseverance and always trust your gut extinct.

Paula Abdul, Performer

I always trust my gut reaction; it’s always right.

Kiana Tom, Television Host

Intuition comes very close to clairvoyance; it appears to be the extrasensory perception of reality.

Alexis Carrel, Nobel Prize Winner (Medicine)

Before making a decision about whether to trust our gut, it seems like a worthwhile endeavor to first try to understand what exactly our “gut” is. There are a number of possibilities:

1. Sometimes gut feelings can be explained by our evolved instincts that are encoded in our DNA, which exist because they helped our ancestors survive in the world as it was hundreds of thousands of years ago. For example, we are likely to feel anxious when confronted with something unfamiliar (a large unknown animal, for example), or feel fear when we hear a loud noise. These sort of reactions are very useful at times, but typically only work well in scenarios involving danger or conditions that are similar to those that our prehistoric ancestors encountered. At a birthday party where balloons are being popped, a fear of loud noises is not useful. On the other hand, when walking in a canyon, a loud noise might indicate a cascade of rocks and a fear response might save your life.

2. In many cases our intuition is associated with our immediate emotional responses to stimuli. For example, we might get a positive feeling towards someone who has a warm smile, or feel negatively towards a person who is raggedly dressed. While our emotional responses clearly are important (e.g. it’s important to feel sympathy towards a friend when they look sad, and to feel fear when encountering someone who has hurt you in the past) they can also be distorted and counter productive. For example, many people feel slighted if a friend fails to return their phone call. However, one is likely to feel better about the situation (despite his initial emotional response) if he reminds himself that there are all sorts of reasons that a friend doesn’t return calls, including being temporarily busy or absent minded. On the other hand, those who trust in their initial response of hurt and anger (which might stem, for example, from a lack of confidence or insecurity) are more likely to blow up at the friend or act coldly during the next encounter, which could damage a generally fulfilling relationship. Unfortunately, it can be tricky to differentiate between emotional responses that are useful and improve our lives, and those that are based on misperceptions and are unhelpful. Both of these types of emotional responses feel equally real when you are experiencing them, and it is often only when we carefully scrutinize them from a neutral point of view that we can tell the difference.

3. Sometimes our “intuition” is based on repeated experience that we access automatically. For example, a surgeon might get an uneasy feeling during an operation, which could be triggered automatically when she notices similarities between the current patient and difficult surgical cases she has had in the past. Another example would be a painter who suddenly has an impulse to add more thinner to the paint he is using, which could be a subconscious reaction based on years of art making experience. Generally when we repeat similar tasks enough times, their execution becomes automatic and begins to feel like an instinct. We might then say that we have developed an intuition for effectively completing the tasks. These kinds of responses can occur much faster than those controlled by conscious thought, and thus can be very efficient and useful. Of course, if the initial learning phase that leads to one’s intuitions is not of good quality (e.g. we complete the task poorly while learning), the intuition will be of poor quality as well. Sometimes intuitions of this form are experienced in emotional form as an uneasy feeling, in particular when our (possibly subconscious) expectations (based on experience, training or practice) do not match what we see. A day trader, for example, might decide to sell a stock due to an uncomfortable feeling about it. In reality, what may have happened is that the stock chart had a pattern that did not conform to his expectations. This intuition can be quite useful since those cases that don’t match our predictions can be especially difficult, require special attention, and present unknown hazards.

4. Societal conditioning can create a kind of gut reaction that operates without conscious awareness. If we are told enough times when we are young not to trust strangers, then we may feel immediately distrustful when a stranger strikes up a conversation. The trouble with responses of this kind is that they are often formed without thought or careful reflection. For example, if we grow up in an area where a lot of racism is present, we might be told that certain races are inherently dishonest, and so could have strong intuitive reactions to people of those races based on this idea. Similarly, if we are taught to believe that black cats bring bad luck, we might start feeling uneasy in a house with a black cat. Since the ideas that society conditions us with may not be true, it can be very valuable to be aware of these automatic reactions and to carefully evaluate their logical and empirical validity.

5. Our brains are capable of forming very strong associations (between perfumes and people, for instance) and this can lead to what might be interpreted as “gut feelings”. For example, if we were attacked by dogs when we were young, we may feel anxious around dogs later in life, even when we know on an intellectual level that we are safe around them. Such associations clearly have a valuable survival purpose, but on the other hand, can push us into self defeating behavior (like refusing to visit the house of a friend because she has a dog). Our brain’s natural tendency is to be “better safe than sorry”, as your ancestors were very unlikely to die from forming spurious associations (such as that dogs are generally dangerous), but were at real risk of dying if they failed to form certain real associations (such as that wolves are dangerous).

As we can see, what people call their “gut” is most likely a hodgepodge of various brain activities, which include survival instincts, emotional responses, automatic recall of learned information, societal conditioning, and associations. It is not at all obvious that these systems will lead to good decision making in general. Each has its very important uses, as well as significant domains where it will fail. A business man cannot rely on fight or flight instincts when giving an important presentation, a person with an anxiety disorder cannot expect his emotional responses to be accurate representations of reality, a doctor cannot rely on his old impulses when learning a totally new surgical technique, and no one can expect that their society will condition them only with true information. Hence, to make truly good decisions, it is essential to evaluate your intuition to make sure that it is likely to be accurate in the situation at hand. Each time our gut tells us something, we cannot know whether to trust it until we understand where that feeling originates from.

1. Do terrorist groups want to nuke the United States?

It seems that yes, there are groups that would be willing to do this. According to the Report of the Commission on the Prevention of WMD Proliferation and Terrorism, “At the moment, al Qaeda is judged to be the sole terrorist group actively intent on conducting a nuclear attack against the United States.” Of course, it is impossible to rule out the possibility that other groups are also seeking to do this. I’m going to work under the assumption that Al Qaeda and those groups tightly connected to it are the only ones that would have the interest and/or capabilities of actually plotting such an attack at this time.

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2. Where would terrorists get nuclear weapons?

Genuine nukes of great destructive power are quite difficult to build, and cost estimates for building full scale weapons (of the 25-35 kiloton variety) seem to be > $5 Billion. Furthermore, such weapons would likely take longer than a decade to build from scratch (though these numbers are a bit old, so the process may have become cheaper as technology has progressed). Hence, it seems highly likely that if terrorists intended to use such a weapon they would steal them, buy them, or get them through strategic arrangements with governments that already have them. Of course, different types of weapons with different yields would have different costs associated with them, and the amount of time that it would take for construction depends on the scale of the project (with more resources and more scientists it would likely go faster). Some people fear that there may be poorly controlled nuclear weapon materials in Russia (such as bomb-grade uranium). Others fear that nukes could be stolen from Pakistan, in part because of the country’s potential instability, and also because it is possible that Al Qaeda is conducting operations there. Iran also could be a potential source of danger, in part because it is run by a religious zealot and it is unclear how far he would be willing to take his anti-American sentiments.

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3. What sort of weapons would terrorists be likely to use?

It would be far, far easier to attack the U.S. with a dirty bomb (a conventional bomb laced with radioactive material in a manner such that the material is spread by the blast) than with a full scale nuclear weapon since dirty bombs are so much easier and cheaper to construct or acquire. Such an operation would also seem to have a much greater chance of succeeding than use of a true nuclear bomb since it does not require recruiting high level nuclear scientists, massive deal making with large nations for supplies, or a laboratory which must be kept secret for a decade or more. The supplies for the construction of dirty bombs are relatively easy to obtain, though these weapons have far less destructive capability than true nukes. There has been at least one known plot (in actuality, probably more like two or three) to detonate a dirty bomb in the United States.

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4. If terrorists did choose to attack the United States with nuclear weapons, how likely would they be to choose Manhattan as their target?

It seems quite likely that if terrorists attempted a nuclear attack on the United States, it would be carried out in either Manhattan or Washington DC. Manhattan is an obvious choice because the County of New York is the most densely populated county in the country, so damage and chaos could be maximized , and because Manhattan has enormous importance to the U.S. economy. DC is also a natural choice because of the opportunity it might provide terrorists to disrupt government operations. That being said, the United States is a huge place, and it is possible that for logistical reasons terrorists might find New York difficult. If I had to put a probability on it, I would guess that there might be a 3 in 10 chance that Manhattan would be chosen as a target.

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5. If terrorists attacked Manhattan with nukes, how bad would it be?

The worst case scenario pretty much would be the detonation of a nuclear bomb (hidden in a truck or in an ocean shipping container). One source (a report by Ira Helfland, head of emergency medicine at Cooley Dickinson Hospital) estimates that a 12.5 kiloton bomb of this nature “smuggled into the port of New York aboard a shipping container and detonated at ground level” would end up killing approximately 260,000 people (about 52,000 of them would die immediately as a consequence of the blast, 10,000 would die soon after from direct radiation exposure, and the remainder would die from nuclear fallout). The study says that that several hundred thousand more would become sick from radiation sickness. There are about 1.6 million residents in Manhattan, which balloons to about 3 million during the day from people traveling into Manhattan. If we assume that the attack occurred during the day (when population densities are highest), and that in total 600,000 either die or get very sick, and that about 2.5 million people are in Manhattan at that moment (since some commuters will have left before the moment the attack occurred, or not arrived yet), then you would have about a 25% chance of dying or becoming seriously ill.

What about the case of a dirty bomb attack? In this case, it’s most likely that fewer than 10,000 people would die or become seriously ill, leaving a probability of less than 0.5% of sickness or death.

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6. What have known terrorists plots on the united states been like?

Since 9/11 muslim extremists have concocted at least fifteen thwarted plots to carry out terrorist attack in U.S. In fact, the true number is probably quite a bit higher than this. The plots that I was able to find by conducting a few quick searches were:

-Shoe bomb in plane.

-Attempted construction of a dirty bomb.

-Blowtorches to collapse brooklyn bridge.

-Attack New York Stock Exchange and construct a dirty bomb.

-Bomb subway station Near Madison Square Garden.

-Assassinate diplomat with grenade launcher.

-Attack national guard facilities, synagogues and other places in Orange County, CA.

-Plot to blow up wyoming natural gas refinery, the transcontinental pipeline, and the NJ Standard Oil Refinery.

-Potential planned attack on the U.S. Capitol and World Bank headquarters.

-Blow up Sears Tower and FBI offices.

-Attack underground transit links connecting to New Jersey.

-Blow up ten commercial airliners.

-Attack U.S. Army base Fort Dix in New Jersey with assault rifles and grenades.

-Blow up jet fuel artery that runs through residential neighborhoods at JFK international airport.

-Attack the Empire State Building and U.S. nuclear power stations.

Note that all of these attacks have been thwarted, either by the incompetence of the perpetrators, or by effective government work. The only “successful” attacks since September 11, 2001 (that might potentially be considered terrorist attacks) that I managed to find in my quick searches were:

-An Egyptian gunman opens fire at an El Al ticket counter in Los Angeles International Airport, killing two Israelis before being killed himself.

-Joel Henry Hinrichs III detonated a bomb near the packed football stadium at the University of Oklahoma in Norman, Oklahoma killing himself in the process.

-Mohammed Reza Taheri-azar, an Iranian-born graduate of the University of North Carolina at Chapel Hill, drives an SUV onto a crowded part of campus, injuring nine.

-An Afghani Muslim hit 19 pedestrians, killing one, with his SUV in the San Francisco Bay area.

-A man attacks Fort Hood with guns, shooting 44 people.

Something to notice here is that most of these attacks on the U.S. since 9/11 have failed or were foiled, and most of the ones that haven’t failed were relatively small scale. What’s more, all of the attacks listed are much, much less complex and difficult and expensive to pull off than building/acquiring, transporting and detonating a full scale nuclear bomb.

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7. What is the (very roughly) estimated probability that a person living in Manhattan will die or become seriously injured/sick by a nuclear weapon attack within the next ten years?

This estimate will of course be very crude and inaccurate, but here goes. First lets consider the case of a full nuclear bomb attack. If such an attack occurred in the U.S. and went according to plan, there might be something like a 3 in 10 chance that it would target Manhattan. The chance of death or serious injury depends a lot on the strength of the bomb, but if we assume a large bomb of about 12.5 kilotons this might give a person in Manhattan a 1 in 4 chance of avoiding serious physical harm. What would the probability be that such a plan would be foiled by the government or botched by the perpetrators? The odds seem very good of this happening, as a great number of much simpler attacks that would involve many fewer people have failed. In fact, only about 1 in 5 of the attacks I managed to find information about succeeded, and the ones that DID succeed were some of the very simplest to organize. I would guess that the odds of the success of a full scale nuclear bomb attack are something like 1 in 100. If this seems low, keep in mind that this figure has to take into account the odds that the terrorists fail to acquire or build the bomb despite their attempts, that they run out of funding, that their facilities are discovered and raided, that their bomb is discovered during transportation, that their bomb fails to detonate, that members of their team lose their nerve, that they can’t get the bomb into the U.S., etc.

The next thing to estimate are the odds that SOME terrorist group is actually attempting to plan an attack like this. The plot would be very difficult and expensive to pull off, but on the flip side, would be massively effective at injuring the U.S. (through death, illness, property damage, and widespread panic), so the difficulty might be balanced to some degree in the terrorists minds by the potential damage caused. The enormous potential cost of this project and the expertise required may well be prohibitive though, so I’ll place the odds that Al Qaeda or a closely linked group would pursue completing this project within the next ten years rather arbitrarily at 1 in 10. Here I am assuming that only Al Qaeda terrorist group would even be willing to attempt such a project. All in all, this very crude estimate indicates that the likelihood that terrorists attempt to attack the U.S. with a full scale nuclear bomb, actually succeed in this plan, carry out this attack in Manhattan, and kill any one particular Manhattan resident (chosen at random) is about 1 in 13,300 (over a ten year estimated period). To put this in perspective, the chance that you eventually die of a car accident (rather than other potential causes of death) is about 1 in 6,800.

On the other hand, dirty bomb scenarios are far more likely to be carried out successfully, and far more likely to be attempted (in fact, they already have been) but are unlikely to actually kill or seriously harm a randomly selected person in Manhattan. We can estimate that, once again, there might be a 3 in 10 chance that such an attack (if it occurred) would occur in Manhattan, that if it did happen in Manhattan each individual would have less than a 1 in 200 chance of incurring serious harm (let’s say for the sake of argument that the most likely number is something like 1 in 400), that such an attack might be planned twice in the next 10 years, and that the chance of success for such an attack might be 1 in 10. These give us odds that a single, predetermined person in Manhattan would suffer serious physical harm from a dirty bomb at about 1 in 6,600. This number is also on the order of the chance of eventually dying from a car accident.

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8. How much should we fear nuclear terrorist attacks if we live in Manhattan?

From the simplistic analysis carried out above, the answer seems to be that Manhattan residents (who plan on staying in Manhattan for just ten more years) shouldn’t fear nuclear terrorism all that much more than a randomly selected American should fear the possibility of dying of a car accident at some point in their life. One thing that may be worth pointing out is that even if a nuclear weapon did kill us, there is some chance (dependent on the characteristics of that weapon) that it would do so fairly instantaneously, meaning that we would be dead before having much opportunity to suffer or even notice, which seems a lot less horrible than a slow death by radiation poisoning. On the flip side though, if a nuclear weapon was detonated and did not kill or injure us, the psychological effects of such a disaster could still be great, potentially causing the death and injury of those people we know, and likely inducing panic.

While nothing is known for certain and this analysis is certainly flawed in a handful of ways, the chance of a nuclear terrorist threat does not seem high enough to warrant moving out of Manhattan if you derive significant value from living there. Moreover, if you have already decided that you are going to live in Manhattan, what is the use of worrying about death from nuclear weapons at all? It isn’t as though worrying is likely to make you safer in a significant way. There are many things that have the potential to kill us each day, and we tend to simply not think about them, so why should this be different? Sure, it seems scarier in some ways than car accidents, which feel more familiar, but car accidents (and tumors and strokes) can be just as horrible as death by nuclear bombs or dirty bombs. Living in fear will almost certainly reduce your quality of life without making you substantially safer, so the best thing is probably to learn to be okay with the fact that we will never be totally safe (from nukes or cars or the huge number of other things that might hurt us), and this is just a part of life.

If thoughts about nuclear weapons are something that you find you are upsetting yourself with frequently, you might try writing down answers to the following questions:

a) If I don’t worry about hundreds of other potential sources of death, then why should I worry about this one source, especially since it is quite unlikely to occur?

b) What advantages and disadvantages are there to my worrying about nuclear bombs (especially taking into account the fact that there is nothing I can do to prevent such an attack)?

c) Since death is inevitable, and often painful and unpleasant, is dying from nukes really such an especially horrible way to go?

d) What is a more productive use of our time, worrying about nuclear bombs or researching and implementing ways to mitigate preventable sources of death? (keeping in mind that most of us could eat healthier, exercise more, wear our seat belts more scrupulously, get more regular checkups, and do many other things that would likely extend our lives).

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