Many years ago, on my old web page, I wrote a piece explaining the twin paradox of special relativity. More recently, I created a YouTube video with the same purpose. Now, I'm not a physicist, and don't claim to have a complete understanding of Einstein's theory at all. I just happened to stumble upon and share a way to think about the twin paradox in a way that made sense to me and that seemed to be consistent with what the experts say about it. (If I'm wrong, of course, I shall be more than happy to have a physicist set me straight on it.)
But a curious thing happens when you post something about relativity theory on the internet. You start getting email or comments from people who are convinced that Einstein was hopelessly wrong, and who try to explain how. Over the years I've had maybe a half-dozen correspondents on the subject. As I said, I'm not an expert, so I'm really not in a position to debate them about the theory generally, but I'm into thinking and reasoning generally, and I'm very interested in diagnosing the kinds of cognitive errors people (myself included) typically make.
In this case, I'm intrigued by the ways in which some people naively take issue with the views of the experts. Most of us, I'm guessing, would look at something like relativity or quantum mechanics, admit that we haven't really got a clue, and defer to the guy in the white lab coat scribbling formulae. But the ones who email me about relativity, at least, almost invariably seem to be convinced that they not only understand it, but understand it well enough to refute it. Relativity is just one example; somewhat more common are the creationists who argue passionately about how Darwin got it wrong. More troubling yet are the various conspiracy theorists, anti-vaxxers, sovereign citizens, climate-change-denialists and other similar movements, which not only are hopelessly confused about the actual subject matter but are actively doing real harm to themselves and others through their ignorance.
Don't get me wrong: I am not saying that one should accept without question whatever The Experts tell us. Sometimes the authorities are wrong, and in any event, we all benefit from healthy dialogue about theories and issues, because even a wrong theory can help bring us to a better understanding of the truth. It's vitally important, in a free and democratic society, that people feel free always to question the conventional wisdom. It's not disagreement with the experts I want to criticize here, but rather methods. There is a right way and a wrong way to be a skeptic.
In this post, I want to talk about the a particular error that's usually a dead giveaway that someone is not so much a brave dissident challenging the hidebound orthodoxy as a deluded crackpot. Specifically, it amounts to assuming that the experts are unaware of basic "common-sense" facts about their discipline.
It's a safe assumption that if something is common knowledge, an expert in the field is probably aware of it. For example, most people know that mercury is very poisonous, as are most heavy metals, so it's reasonable to assume that an expert in chemistry or medicine will also be aware of this basic fact. I suppose you might find some expert who believes mercury is harmless, but at the very least, even that expert should be aware of the widespread belief that it's poisonous, and be accustomed to having other people disagree on that point. If you tell someone that mercury is poisonous, the expert might say, "Yes, it is," or give an exasperated sigh before patiently explaining how that's a common misconception.
Yet anti-vaxxers will exclaim in alarm that vaccines contain mercury! MERCURY, for heaven's sake! I'm not sure how they expect physicians to react to this revelation: "Wait, what? I thought thimerasol was just a preservative! Good heavens, there's mercury in it? And mercury is poisonous?Why didn't anyone say something?!"
Give them some credit. They already knew that mercury is poisonous, and that thimerasol contains mercury, when they decided to use it. Just like a surgeon knows that stabbing someone with a knife is usually bad for them. And yet somehow, the surgeon knowingly goes ahead and cuts people open with a knife in order to treat them, because they know a heck of a lot more about cutting people and putting them back together than a random layperson does.
That's the thing about experts. They don't just know the really simple obvious stuff that everybody knows; they also know a bunch of complicated stuff that occasionally flies in the face of the obvious overgeneralization. Yes, cutting someone with a knife is usually bad for them, but it can be made less bad with proper preparation, tools and technique, and sometimes it's much less bad than leaving the condition untreated.
Lots of things are obvious to everyone, expert and non-expert alike. But if we could rely on the obvious in all instances, we wouldn't need experts at all. Experts are those who understand the non-obvious parts of their disciplines as well as the obvious, the things that not everyone knows. So if your criticism of the experts is based on their apparently overlooking something really, really obvious, stop. Do not assume they're idiots for missing what is plain to you, and tell them they're wrong. That is how crackpots act, and rightly or wrongly, you will be dismissed as one.
Instead, ask. "Wait, I thought mercury was poisonous? Why are you putting it in a vaccine?" Because then they can explain how the toxicity is much less when the mercury is tied up in certain kinds of molecules, and how the quantity involved is so tiny that even if it poses any risk it's far outweighed by the benefits of the vaccination itself, and if you've the time and patience they can go through the data with you and eventually you'll understand it like an actual expert yourself. Or, they might do what they actually did with thimerasol: "Well, it's actually quite safe, but since you're concerned about it, we can replace it with something that doesn't contain mercury."
Another way to put it is like this: it's okay to disagree with someone, but it's not okay to disrespect them, and assuming someone is so stupid as to be completely unaware of common sense notions of her area study is fundamentally disrespectful, and empirically wrong. Common sense does not trump expert knowledge. You don't have to believe the experts, but don't presume they're idiots.
Friday, 20 March 2015
Tuesday, 3 March 2015
Root Canal, Cancer, and Terrorism
Last year, I wrote a bit of satire applying some of the same arguments I've heard about abortion to root canal, in an attempt to show just how silly it is to bring moralizing arguments to bear on medical procedures. If someone needs treatment, they need treatment, and it's too late to argue about whether or not they ought to have engaged in the behaviour that led to that need. You can certainly argue about whether or not they do need the treatment, or whether the procedure itself is morally acceptable, or you can call attention to the risks and side effects involved, but that's a very different thing from saying, "Well, you should have thought of that before you [had sex/ate candy/went bungee-jumping/dressed that way]!"
Anyway, in that piece, I alluded to this claim that root canal causes cancer, which is apparently still in circulation because a friend forwarded it to me recently. The big, bold headline:
First of all, the statistic isn't actually all that reliable. If you read the article, the source turns out to be a Dr. Issels, who simply recounts that in his 40 years of practice that many of his terminal cancer patients had the procedure. And maybe that many did, although it's just as likely he picked "97%" to emphasize "a lot". This is not a careful clinical study; the actual number could be wildly off.
Even if the number isn't wildly off, it still doesn't mean anything other than that most of Dr. Issel's terminal cancer patients had had the procedure. There's no reason offered to think that 97% of all terminal cancer patients everywhere have had root canal. There could be any number of reasons why Dr. Issels' patients had a higher than average rate; perhaps he got a lot of referrals from an endodontist friend. Or perhaps the kind of person who puts off going to the dentist until a root canal is necessary is also likely to put off getting checked out for cancer until it's terminal. Or, maybe it's just that anyone who lives long enough to develop cancer has also lived long enough to make the odds of having had a root canal pretty high, as well.
But that's only part of the problem with this statistic. Let's just assume for the sake of argument that it's completely accurate, that 97% of all terminal cancer patients have had a root canal operation. By itself, this still means nothing, because we have nothing to compare it against: how many people without cancer have had root canals? According to the article itself, 41,000 root canal procedures are performed in the U.S. every day. (This is probably the source for that claim.) That's 15 million a year, for a population of 300 million people; on average, that means each person has one every 20 years. Obviously, some have more than their share, and many have none, but the point here is that root canals are extremely common. If 97% of everybody has had a root canal, then the fact that 97% of cancer patients have had it should come as no surprise. (Of course, for the reasons in the previous paragraph, I'd actually expect cancer patients to have had a somewhat higher rate of root canal than the population at large, if only because they tend on average to be old enough to have lost their baby teeth.)
Enough of the statistics. Now some lay-person's background on the science. Root canal is basically a massive filling, where decayed bits of tooth are drilled out and replaced with artificial material. The difference is that in a routine dentist-visit filling, the cavity only goes into the outer layers of the tooth, and can be quickly patched up with a bit of gold or amalgam or whatever it is they use these days. In a root canal, the decay has reached into the softer living tissue inside where there are nerves and blood vessels and especially nerves, which is why ouch. So in a root canal, they have to clean out all that infected softer tissue, and then fill it all in with something to keep the rest of the tooth from breaking in when you chew. In the bad old days, they'd have to just yank out the whole tooth, but this is a way of saving as much of your original dentition as possible.
So the claim in the article is that bacteria gets into the filled-in core of the tooth, and festers there, releasing toxins into your blood which cause cancer. I should say that this is not by itself completely ridiculous, because there are all sorts of things that can cause cancer, including viral and presumably bacterial infections. There's no reason to rule out the possibility that a long-term infection in the body (whether in a tooth or a bone or a wart or whatever) could promote cancers. And we know that abscesses are really nasty in lots of other ways (which is why we often need root canals in the first place).
The part that doesn't make much sense, though, is how this is supposed to relate to root canals specifically, especially on the scale implied by the shock-inducing 97% claim. The problem is that if the filled-in tooth canal is sealed off enough to allow anaerobic bacteria to thrive, then it's probably also sealed off enough to keep them and their toxic byproducts away from the bloodstream.
Moreover, bacteria are like any other living thing: they need energy, which those of us who can't photosynthesize have to get by eating things. So sealing off nasty microbes inside the tiny spaces of a tooth might give them a nice hiding place for a while, but they'd exhaust the available nutrients in there pretty soon, and then they'd starve.
Of course, there may be just enough circulation of fluids to bring in a little food for the bacteria, to keep them alive, but that kind of bare subsistence infection isn't going to be able to do you much harm, either. The conditions after a root canal are not special, and there are no doubt many little colonies of germs trying to establish a foothold throughout your body at any given time. This is natural, and typically they don't last long, because we have immune systems. A big infection, like in an abscess, can overwhelm the defences, but a microscopic one is a pretty routine event, and at most a successful root canal replaces a huge potential abscess with some negligibly tiny germ hangouts.
This is the thing that so many health panics don't seem to understand: germs are freaking everywhere. They aren't harmless at all, and they're trying to kill us all the time. But that's no big deal; that's how it's always been, and our immune systems and repair mechanisms are awfully good at what they do. They are more than capable of dealing with a Hole-In-The-Wall gang of bacteria hiding out at the site of a root canal, because they're always dealing with that sort of thing. Whether or not you've ever had a root canal, your immune system is right now dealing with exactly the same kinds of invaders and their associated toxins from some other source.
The same argument applies to the mercury they once used as a preservative in vaccines, the fluoride in our drinking water, and a host of other unpleasant chemicals. Yes, we should try to minimize our exposure to these things, but when the amount we're worrying about is drowned out in the background noise of what our bodies are used to dealing with, it's time to go worry about something else. We are much better off trying to reduce that background noise than we are obsessing about a trivially small component of it. (Especially when it comes to things like root canal, fluoridation and vaccines, things which are specifically meant to give net health benefits that far outweigh whatever trivially tiny risks they might carry.)
Which brings me to terrorism. Yes, terrorism exists, but it's really just a particular form of violence. There are, and perhaps always will be, people who believe that violence is a way to solve their problems. Sometimes they just get angry and lose control, or sometimes they coldly calculate that someone's death will bring them an insurance payoff, or sometimes they fall prey to a radical ideology. Whatever the cause, it's bad, but our civilization has developed systems for dealing with violence. People commit crimes, the police track them down, they stand trial, they go to prison. It's not ideal, but it generally works to keep us relatively safe (and it's worth repeating that we live in the least violent time in human history.)
The reason we shouldn't worry about terrorism is the same reason we shouldn't worry about getting cancer from a root canal: the actual incremental risk of being hurt or killed by a terrorist is many orders of magnitude lower than your already low risk of being a victim of criminal violence generally. We will do much more to improve our safety from violence, including terrorism, by adopting policies and attitudes which serve to make ours a more just, more compassionate, more connected community, in in which people do not become so alienated and disenfranchised that they turn to violence as a way of affirming their significance.
Anyway, in that piece, I alluded to this claim that root canal causes cancer, which is apparently still in circulation because a friend forwarded it to me recently. The big, bold headline:
especially caught my eye, as of course it was meant to. You might think, given that I had a root canal about thirty years ago, and that I had a cancer that would have been terminal but for timely surgery, that I'd be inclined to find this at least credible. And yet, I'm unimpressed.97% of Terminal Cancer Patients Previously Had Root Canal Procedure
First of all, the statistic isn't actually all that reliable. If you read the article, the source turns out to be a Dr. Issels, who simply recounts that in his 40 years of practice that many of his terminal cancer patients had the procedure. And maybe that many did, although it's just as likely he picked "97%" to emphasize "a lot". This is not a careful clinical study; the actual number could be wildly off.
Even if the number isn't wildly off, it still doesn't mean anything other than that most of Dr. Issel's terminal cancer patients had had the procedure. There's no reason offered to think that 97% of all terminal cancer patients everywhere have had root canal. There could be any number of reasons why Dr. Issels' patients had a higher than average rate; perhaps he got a lot of referrals from an endodontist friend. Or perhaps the kind of person who puts off going to the dentist until a root canal is necessary is also likely to put off getting checked out for cancer until it's terminal. Or, maybe it's just that anyone who lives long enough to develop cancer has also lived long enough to make the odds of having had a root canal pretty high, as well.
But that's only part of the problem with this statistic. Let's just assume for the sake of argument that it's completely accurate, that 97% of all terminal cancer patients have had a root canal operation. By itself, this still means nothing, because we have nothing to compare it against: how many people without cancer have had root canals? According to the article itself, 41,000 root canal procedures are performed in the U.S. every day. (This is probably the source for that claim.) That's 15 million a year, for a population of 300 million people; on average, that means each person has one every 20 years. Obviously, some have more than their share, and many have none, but the point here is that root canals are extremely common. If 97% of everybody has had a root canal, then the fact that 97% of cancer patients have had it should come as no surprise. (Of course, for the reasons in the previous paragraph, I'd actually expect cancer patients to have had a somewhat higher rate of root canal than the population at large, if only because they tend on average to be old enough to have lost their baby teeth.)
Enough of the statistics. Now some lay-person's background on the science. Root canal is basically a massive filling, where decayed bits of tooth are drilled out and replaced with artificial material. The difference is that in a routine dentist-visit filling, the cavity only goes into the outer layers of the tooth, and can be quickly patched up with a bit of gold or amalgam or whatever it is they use these days. In a root canal, the decay has reached into the softer living tissue inside where there are nerves and blood vessels and especially nerves, which is why ouch. So in a root canal, they have to clean out all that infected softer tissue, and then fill it all in with something to keep the rest of the tooth from breaking in when you chew. In the bad old days, they'd have to just yank out the whole tooth, but this is a way of saving as much of your original dentition as possible.
So the claim in the article is that bacteria gets into the filled-in core of the tooth, and festers there, releasing toxins into your blood which cause cancer. I should say that this is not by itself completely ridiculous, because there are all sorts of things that can cause cancer, including viral and presumably bacterial infections. There's no reason to rule out the possibility that a long-term infection in the body (whether in a tooth or a bone or a wart or whatever) could promote cancers. And we know that abscesses are really nasty in lots of other ways (which is why we often need root canals in the first place).
The part that doesn't make much sense, though, is how this is supposed to relate to root canals specifically, especially on the scale implied by the shock-inducing 97% claim. The problem is that if the filled-in tooth canal is sealed off enough to allow anaerobic bacteria to thrive, then it's probably also sealed off enough to keep them and their toxic byproducts away from the bloodstream.
Moreover, bacteria are like any other living thing: they need energy, which those of us who can't photosynthesize have to get by eating things. So sealing off nasty microbes inside the tiny spaces of a tooth might give them a nice hiding place for a while, but they'd exhaust the available nutrients in there pretty soon, and then they'd starve.
Of course, there may be just enough circulation of fluids to bring in a little food for the bacteria, to keep them alive, but that kind of bare subsistence infection isn't going to be able to do you much harm, either. The conditions after a root canal are not special, and there are no doubt many little colonies of germs trying to establish a foothold throughout your body at any given time. This is natural, and typically they don't last long, because we have immune systems. A big infection, like in an abscess, can overwhelm the defences, but a microscopic one is a pretty routine event, and at most a successful root canal replaces a huge potential abscess with some negligibly tiny germ hangouts.
This is the thing that so many health panics don't seem to understand: germs are freaking everywhere. They aren't harmless at all, and they're trying to kill us all the time. But that's no big deal; that's how it's always been, and our immune systems and repair mechanisms are awfully good at what they do. They are more than capable of dealing with a Hole-In-The-Wall gang of bacteria hiding out at the site of a root canal, because they're always dealing with that sort of thing. Whether or not you've ever had a root canal, your immune system is right now dealing with exactly the same kinds of invaders and their associated toxins from some other source.
The same argument applies to the mercury they once used as a preservative in vaccines, the fluoride in our drinking water, and a host of other unpleasant chemicals. Yes, we should try to minimize our exposure to these things, but when the amount we're worrying about is drowned out in the background noise of what our bodies are used to dealing with, it's time to go worry about something else. We are much better off trying to reduce that background noise than we are obsessing about a trivially small component of it. (Especially when it comes to things like root canal, fluoridation and vaccines, things which are specifically meant to give net health benefits that far outweigh whatever trivially tiny risks they might carry.)
Which brings me to terrorism. Yes, terrorism exists, but it's really just a particular form of violence. There are, and perhaps always will be, people who believe that violence is a way to solve their problems. Sometimes they just get angry and lose control, or sometimes they coldly calculate that someone's death will bring them an insurance payoff, or sometimes they fall prey to a radical ideology. Whatever the cause, it's bad, but our civilization has developed systems for dealing with violence. People commit crimes, the police track them down, they stand trial, they go to prison. It's not ideal, but it generally works to keep us relatively safe (and it's worth repeating that we live in the least violent time in human history.)
The reason we shouldn't worry about terrorism is the same reason we shouldn't worry about getting cancer from a root canal: the actual incremental risk of being hurt or killed by a terrorist is many orders of magnitude lower than your already low risk of being a victim of criminal violence generally. We will do much more to improve our safety from violence, including terrorism, by adopting policies and attitudes which serve to make ours a more just, more compassionate, more connected community, in in which people do not become so alienated and disenfranchised that they turn to violence as a way of affirming their significance.
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