Michael Shermer on What is Truth, Anyway?

welcome to another lecture of skepticism 101 this lecture is on what is truth anyway this is actually one of the earliest lectures in the course usually lecture number two or three and it's based on one of my scientific american columns which was titled what is truth anyway and that particular one of course like all my columns are just one page and scientific americans up to 700 words i just addressed really how we know what is true very briefly and then got into the subject of the resurrection that was my easter column so i want to dive into this much deeper actually since i was just touching the surface there of what really is epistemology it's the study of how we know what we know which is a huge subject i'm not a professional philosopher so i'm coming at the subject of truth um and how we know it uh from a skeptics and scientific perspective through the lens of skepticism so let's begin by distinguishing three different types of truth claims the first is subjective internal truths for example dark chocolate is better than milk chocolate now i happen to think that that's an objective external truth but i recognize that uh there are other people that swear milk chocolate is the objective external truth and there's no test we're going to run to determine which is the better one so that would be an example of a permanently subjective internal truth or as i like to say stairway to heaven is the greatest rock song of all time now i know i know what you're thinking free bird yes free bird is great it's not as good as stairway to heaven but again i know people that think free bird is better than stairway to heaven so there's no experiment we're going to run or test where we're going to conduct or data we're going to collect to determine which is the truer song so those are strictly internal then there's subjective truths that may become objective truths for example meditation makes me feel better is a subjective internal truth it just works for me i don't know if it works for you i'm just saying it works for me it's true for me what people like deepak chopra want to claim or want to shift meditation is to an objective truth that it works meditation works and by work what we're after here is not just for me but for you or sixty percent of the people that tried meditation for one hour a day for six months had lower rates of chronic pain or migraines or blood pressure or stress hormones or or whatever your qualitative quantitative measure is that you're using to test that claim but that's the idea that like in medicine it's not enough to just say well you know the retroviral drugs work for me but not for anybody else or they're true for me no we want to know do they really work this case for aids patients or aspirin really works to knock back um headaches at this level at this measure for this time and so forth that's what we mean by work so most of what we care about in science and medicine in engineering too is does it really work not just does it work for me or for you personally but really that's an example of the subjective truth that we want to make an object of truth and that's one of the goals of science is to apply the tools we have to to arrive at that then there are objective external truths like this example i usually give when i'm sitting there in class there are x people here today just count them up and that's either true or false by observation or i might say dinosaurs went extinct around 65 million years ago this is true how do we know it's true it's true by verification and replication of radiometric dating techniques for volcanic eruptions above and below dinosaur fossil bed so you have a a bedding plane with the dinosaurs that died say they just got buried in a mudslide or something and there was a volcanic eruption before they lived down here and then there's another volcanic eruption after they lived up here and we can date those volcanic eruptions through radio car radiometric dating techniques uh like potassium argon is is an example that measures in the millions of years and so we can say look by these observations plus or minus a little error bar measurement um a variation there but within say 64.9 and 65.1 million years ago these fossils were of living organisms that lived then something like that and that's by the way a good example of how a historical science is a science it's not just a mythic story it's more than that or that the universe began with a big bang how do we know that's true well it's true by a convergence of evidence from a wide range of phenomena such as the cosmic microwave background the abundance of light elements like hydrogen and helium the distribution of galaxies and the large scale structure of the cosmos and the redshift of most galaxies and of course the expansion of space and time so when i was in college the big bang theory had just kind of over took the steady state theory these were two models that were in competition for decades and by the early 70s it was clear that the big bang theory uh was much better closer to truth than the steady state theory by these uh convergence of evidence from these multiple lines of independent inquiry okay that's a that's an important concept in determining what's true what is true is that if you have independent lines of of inquiry that all point to the same conclusion even though they are different sciences they're conducted by different people so this weeds out a lot of the experimental bias or error that might creep into one particular line of inquiry unlikely to do so over multiple lines of inquiry this by the way is how we know climate change is real and human caused okay now these propositions are true in the sense that the evidence is so substantial it would be unreasonable to withhold one's provisional assent this is a slight modification of stephen j gould's definition of a fact i'm broadening the concept to truth and so for example it's not impossible that the dinosaurs died recently just after the creation of the universe ten thousand years ago as young earth creationists believe but it's so unlikely that we need not waste our time considering it therefore i'm defining truth as a claim for which the evidence is so substantial it would be unreasonable to withhold one's provisional assent a claim for which the evidence is so substantial it would be unreasonable to withhold one's provisional assent like gravity this was gould's example it's possible apples will rise instead of fall tomorrow because we don't properly understand gravity say but it's so unlikely that we need not waste our time considering it so the key here in this term is provisional these are provisional truths with a small t truth because in science there are no proofs as in mathematics or capital t truths and there are many reasons for this the first is hume's problem of induction so the great scottish enlightenment philosopher david hume wrote extensively about epistemology and how we know what we know and he pointed out the problem of inductions that is no matter how many white swans or sunrises you see you cannot conclude that there are no black swans or that the sun won't rise one day and in fact there are black swans they're in australia so if you never went to australia you'd think well there are no black swans all swans are white but not all swans are white and although the sun will rise tomorrow and the next day and so on uh in many billion years from now it won't be rising it'll just be expanding out to the point where it engulfs the earth and there'll be no more sunrises at least on earth so let's talk about hume for a minute just a little sidebar here on human causality so when we want to determine what's true what we want to know is what it what is the cause of things or as i like to say colloquially what the hell is going on okay so hume starts off by defining causality that is uh one thing causes another uh is what he called a constant conjunction so a is in conjunction with b now the mind automatically assumes well a cosby this happens all the time we know uh people that think vaccines cause autism because they had their kid vaccinated and shortly after they had some side effects or something and they were diagnosed by their doctor the child was as having autism so the parents just put together a and b well let's see what's the last thing i did we got them vaccinated ah that's the cause of autism that's the assumption you already see the problem with this okay that may not be the case so the silliest example is you know the rooster crows and the sun rises back to sunrises of course they're not caused the rooster is crowing is not causing the sun to rise they are in conjunction yes but not necessarily in causal connection same thing with coffee drinkers are more likely to have heart disease or coffee drinking is associated with or correlated with heart disease but that doesn't mean that there's a cause connection causal connection there for example coffee drinker drinkers also smoke more they exercise less i'm just making that up i actually don't know if that's true or not but if it was true that would be a spurious correlation or what's called an epiphenomenon or confounds or nuisance variables and so the most of the structure of the scientific methodology of experimentation is to get around this problem of epiphenomenon compounds compounds and nuisance variables so much of statistical analysis that you'll hear researchers talking about like controlling for age or controlling for socioeconomic class and then this variable goes away this one increases or whatever what they're trying to do there is get rid of the compound so they can just find the cause that they're looking for this turns out to be much more difficult than anyone realized and then in the second definition of causality hume uh presented the counterfactual idea or definition of causation as hume wrote we may define a cause to be an object followed by another that's constant conjunction or in other words where if the first object had not been the second never had existed so this is a counterfactual it's sort of a thought experiment if we take out the first with the second thing if you if you remove a would b happen so in this case we know that vaccines don't cause autism because if you remove in this case the allegedly contributing factor in vaccines mercury as the alleged causal cause causal agent of autism autism still occurs so by removing the first factor a and b still happens then you determine that by this counter factual that a is not the cause of b so this is known as a counter factual theory of causation it's something of an alternative world if the cause had not happened then the effect would not either so this alternative world or counterfactual so for example if the rooster doesn't grow does the sun rise why yes it does so obviously the rooster crowing is not the cause of the sunrise in this case they have confounding variables in there and non-coffee drinkers who smoke also have heart disease so it isn't the coffee it's something else or a more current topic that is of interest to me is does eating meat cause heart disease is those of you who have listened to my podcast know i go on and on about this because i have heart disease in my family so i'm super careful about exercising and what i eat and it's not clear to me that eating meat is bad in fact i think now maybe it's probably good but that didn't used to be the case it used to be the case that the theory was that heart disease eating meat causes heart disease okay so this is an example of how difficult it can be to determine cause causality even something is obvious that we take for granted today smoking causes lung cancer a causes b not always there are people that smoke their whole lives and they live to be a hundred and they never get hurt they never get cancer okay so obviously there's other variables at work but of course we can conclude that there is a causal connection of some kind it increases the probability of getting lung cancer and so on so right there you see that we're adjusting the formula by adding probability estimates uh to the different compounding variables so these confounding variables must be controlled right so let's talk about causality and truth again we've defined truth here in this lecture as a claim for which the evidence is so substantial it would be unreasonable to withhold one's provisional assent well to do that that requires understanding causality and assessing the likelihood that a causes b or in this case does x cause y that is what's the truth about the relationship between x and y so i'm using x and y now instead of a and b because i want to talk about correlation for a moment again colloquially as i like to say what the hell is going on about x and y so a and b is i use because a simple example of association learning that is connecting a to b is classical and operant conditioning you know so skinner's rat presses the bar and he gets a reward for that that's operant conditioning i can shape him into making that connection between a and b pressing the bar generates a pellet in the little cup and since we haven't fed him since yesterday he's hungry therefore highly motivated to find some connection that'll get him food once he does that's operant conditioning but more broadly it's association learning he's connected a to b classical learning of course is pavlov's dog you ring the bell you give him some food he salivates you ring the bell you give him some food he salivates during the belly salivates he's associated a with b now of course ringing the bell doesn't generate food directly but indirectly it does so there's compounding variables in there does a cause b as pattern seeking primates when we associate a with b we tend to think that this correlation is causation but this is a problem in most of the world because correlation does not necessarily imply causation and determining that is much harder than you think um so how so correlation is how two dependent random variables co-relate which is where the word comes from this goes back to francis galton and spearman in the late 19th early 20th century developing the science of mathematics of correlation but in in roughly speaking for each unit the value of one variable depends on the value of the other variable so they both go up and down in some kind of seemingly causal way this is best visualized in a scatter plot in which two variables appear co-related so for example i love the data graphs from max roser's our world and data website one of the very best and here he's simply run a correlation between life expectancy at birth how many years you will live if you're born in this year this year this year and this year or in this case this country or this country or this country and so the um the horizontal variable there is liberal democracy so as you can see there's kind of a a a line in this scatter plot that runs right through say india and brazil slovakia united states all the way up to sweden on the upper right-hand corner there so although it's scattered so it's not a perfect correlation clearly there's some relationship between uh living in a liberal democracy and living a longer life now it's not perfect and the reason for it's being scattered is because there's confounding variables there's other factors that work here other intervening variables that cause the life expectancy numbers to go up or down of course that could have something to do with the environment and and pollution diet and a bunch of other things but that's an example of a scatter plot that's nicely done in case of max he added the size of the population by making the circles larger or smaller and so on so how do we go from correlation to causation a is co-related or correlated with b but does a cause b maybe but maybe b caused a maybe there's a reverse causation or maybe some third factor we're not thinking about c caused a and b again more compounding variables so for example exercise is correlated with weight loss so one hypothesis is that exercise causes weight loss but i think that's true but it's obviously not the only variable because i mean i work out a lot but my weight varies up and down depending on other factors so another one might be losing weight causes people to exercise well that's right when i lose weight i start exercising i start eating better and therefore i exercise even more because i can see wow i'm dropping pounds that feels great i'm gonna up the ante here on how much i exercise in fact i think i'll be more careful about my diet and so on so or better nutrition here cause both weight loss and exercise or more to the point all three of these factors are at work at any one time and that's just three variables so i'm not going to in this lecture i'm not going into the statistics about all this because it gets really messy and complicated but the point is is that to determine causality to know the truth about this claim about exercise and weight loss that is to figure out what the hell is going on when you're exercising and losing weight we have to take into account all these different factors and more because most effects have multiple causes so with compounds you have a is correlated with b c d e f and g and so on so health is correlated with income education iq parental income neighborhood culture pollution diet exercise lifestyle these are all the different factors that go into that scatter plot i showed you just a minute ago this is why it appears that scientists don't know what the hell they're talking about when they talk about say the food pyramid you know meat is bad no it's good no it's bad uh you know butter eggs up and down it's good and bad it's well which is it coffee good or bad and so on the reason this happens is because there's all these different variables and they're hard to control for in experiments because really mostly you can't do experiments like this except on say prison populations where you can control exactly what they eat instead what you have to do is measure what people are doing naturally and look at the outcome differences between say neighborhoods or age groups or gender race whatever you're interested in studying and all these different factors come into play so take something like stop and frisk since that's on everybody's mind these days with the black lives matter movement um this was very probably a very bad idea but it was difficult to to discern that it didn't work that it was a bad idea i don't just mean morally a bad idea but does it work work to reduce crime the problem is is that crime was up way up before stop and frisk was introduced in fact that's why it was introduced and then crime went down after stop and frisk was implemented here i'm talking about new york city again the problem is does stop and frisk cause crime to go down the problem is that crime was going down for centuries for other causes then it went up in the 1960s through 1993 then returned to its normal long-term decline so in other words the graph kind of goes like this you know it's like down down down down down down whoop a little blipper in the 60s 70s and 80s and then back down through the 90s so if you implement stop and frisk at the peak or just before the p well that's about when they did it just close to the peak and it starts to go down you think well stop and frisk is working no you can't conclude that okay correlation is not causation in fact it was a spurious correlation so not causal how to control for confounds well the gold standard going from correlation to causation is the randomized controlled trial that is you randomly assign a group of subjects in different conditions like diet and cardiovascular disease where people are randomly assigned to the meat group and the vegetarian group and people are randomly assigned to the exercise group in the non-exercise group and as i mentioned before this is difficult to do because it's hard to control for compounding variables people forget what they ate they lie about what they ate they only went to mcdonald's once a week and they say they never went to mcdonald's and so on and so forth or they tell you i work out two hours a day in fact they work out 30 minutes a day or something two hours is a lot i know because that's about what i do and it takes a long time to to put in two hours so people you know in their minds they forget or they exaggerate so those are the kind of compounding variables that make it also these are the kind experiments you can't really do they're mostly unethical again unless you have a population of prisoners or something like that i like this little new yorker cartoon here the title of my science project is my little brother nature or nurture the other funny line about that is you know nature and nurture either way it's your parents fault so how to control for these compounds well these confounds are natural experiments like smokers and health outcomes identical twins reared apart compared to reared together i missed one there 50 yeah okay so like so blue zones and longevity okay you can't force people to eat certain things in entire nations but we can look at different nations or say geographical regions around the world find the group that's living the longest and then go study them what are these people doing in this case they they walk a lot they exercise they eat like a mediterranean diet they have a lot of friends they have a good social safety net and network and other things like that or think about the 50 different states these are 50 different natural experiments they all have all 50 states in the united states have different constitutions so they have different laws except for those that are controlled by the federal government like say abortion is legal in all 50 states gay marriage is legal in all 50 states and so on but gun control laws vary from state to state tax rates vary from state to state some taxes some states have no income taxes and some have no um sales tax and so on so you can look at the outcomes say carrying concealed law differences across different states or counties within states and they make comparisons those are natural experiments or identical twins reared apart okay you can't separate infants and and have them rear in different environments that would be not only unethical it would be illegal so but this is this happens so you see what already happened and what the outcome differences were and you control say identical twins rear depart to identical twins reared together and then you compare that to say fraternal twins rear to part versus rear together then you look at siblings reared together versus rear to part and then complete strangers say adoptees raised in the same family and then you can make comparisons about outcomes like you know rates of smoking or personality temperament measures like the big five or you know weight you know just hundreds of different things you can measure and in general what we find is that uh biosiblings reared together when you compare identical twins or depart to bio siblings rear together and adopt these rear together the correlation is pretty high it's about 0.5 to 0.9 this is say 50 to 90 percent of the variance between people on the particular measure you're interested in and this is like iq levels of happiness and self-satisfaction personality characteristics like openness to experience conscientiousness agreeableness these are a highly correlated between identical twins reared apart so that tells us that the genetic component is very high in for these particular traits or it's a weird example fox news and conservativism from 1996 to 2000 it was randomly introduced by cable companies into 20 of towns and those voted conservative 0.4 to 0.7 percent more so in other words it looks like not just that conservatives are more likely to watch fox news although that's true that there's at least some reason to believe that watching fox news makes you more conservative by these early experiments experiments a naturally occurring phenomenon that people can collect data on and look at the outcomes my favorite example of a natural experiment is north korea versus south korea here is a chart this is from my book the moral arc in which i'm looking at the relationship between per capita gdp in 1990 dollars and across the last half century or more more than half century as measuring their per capita gdp [Music] that is to say both were highly correlated north and south korea all the way up into the early 1970s to the mid-1970s when they diverged with different governments south korea became a democracy and instituted free enterprise free market capitalism more than they had before and north korea has you know moved ever more into the kim dynasty of of a draconian autocracy or dictatorship and the results are staggering this is in let's say when i did this calculation in 2015 eleven hundred dollars per year per person in north korea nineteen thousand six hundred dollars per person per year in south korea that the disparity is even wider now i think it's last time i checked it was like 25 30 000 a year for south koreans versus north koreans that are now into triple digits below a thousand a year you can see the difference it makes from space south korea on the left bottom there and north korea on the top or you can see the difference in heights i mean income per capita gdp income buys you better food buys you better education better schooling better everything really but that's a difference of of course we can't force countries to become dictatorships or free market uh economies but we can measure what happens to countries that do this naturally okay that's that's a good example of natural experiments all right let's return to david hume and again trying to determine what the hell is going on here hume's principal proportionality is an important element here a wise man proportions his belief to the evidence proportionality and of course what he has in mind here when he wrote his treaties on human understanding 1758 in the section on miracles he's talking about the resurrection here here's what he writes about this nothing is esteemed a miracle if it ever happened in the common course of nature it is no miracle that a man seemingly in good health should die on a sudden because such a kind of death though more unusual than any other has yet been frequently observed to happen but it is a miracle that a dead man should come back to life because that has never been observed in any age or country okay so somebody who drops dead that's unusual but it's not a miracle because that does happen somebody who does the opposite they raise from the dead that's never happened we've never seen that so the claim that it is that it has happened once well that would be an extraordinary claim and you know what i'm getting to with this so uh this is what i call hume's maxim this is the next passage in that section the plain consequence is and it is a general maxim worthy of our attention that no testimony is sufficient to establish a miracle unless the testimony be of such a kind that its falsehood would be more miraculous than that the fact than the fact which it endeavors to establish hume continuing quote when anyone tells me that he saw a dead man restored to life i immediately consider with myself whether it be more probable that this person should either deceive or be deceived or that the fact which he relates should really have happened i weigh the one miracle against the other and according to the superiority which i discover i pronounce my decision and always reject the greater miracle if the falsehood of his testimony would be more miraculous than the event which he relates then and not until then can he pretend to command my belief or opinion okay it's a very 18th century way of writing it's it's there's a lot packed in there let's look at it a little more carefully hume's definition of miracles is a violation of a law of nature as he writes a transgression of a law of nature by a particular volition of the deity or some invisible agent in other words for hume a miracle is simply an event caused by god however philosopher david kyle johnson my friend and colleague who has by the way a great teaching company course one of the great courses on philosophy he deals with these kinds of questions clarifies a miracle as for any given event if we knew that god took special care to cause it we would and should cause that even call that event a miracle regardless of whether it involved the violation of natural law so i think uh johnson has made an important addition to hume which for a philosopher that's big hume's huge uh because it isn't just that it's done by the deity uh sorry it isn't just that it's a violation of natural law because you could think of other examples of that that perhaps million to one odds do happen a lot uh so how do you know that there are no exceptions to all natural laws instead it's the the implementation by the deity anyway continuing let's look at this particular case of the miracles of jesus so jesus of nazareth existed that's not an extraordinary claim lots of people yeshua was not an unusual name at that time in that area of the world that jesus was crucified is also not an extraordinary claim the romans crucified everybody i mean just even jesus crucifixion the two criminals on either side of them were pickpockets okay they just had big fun uh crucifying people on the weekends okay i'm kidding but that he walked on water turned water into wine turned mud into sparrows raised the dead and was resurrected those are extraordinary claims because we never see people walk on water or turn water into wine or turn mud into sparrows or raise the dead or be resurrected okay i've seen magicians walk on water pen and teller i've seen ben and delaware turn water into wine i think actually i think it's a copper field do that but of course we know they're tricks right this is why we're uh this is again why the important element of you know violating natural law or the in the intervention of a deity is important in this so there's two possibilities here it really happened jesus really walked on water turned water into wine raised was raised from the dead and so on or the witness narrator of the story of this these accounts is mistaken or lying or exaggerating or hallucinating or they misreported or they saw a conjuring trick or whatever which one is more likely okay we have no experience of ever seeing anyone raised from the dead rise from the dead we have lots of experience and examples of p people mistakenly describing something exaggerating people lie all the time they hallucinate they misreport even if it's honest and we know there's magicians that can do most of these things now let's put it in context how extraordinary is the claim that jesus rose from the dead of the hundred billion people who lived before us all have died and none returned so the claim that one of them rose from the dead is truly extraordinary how extraordinary a hundred billion to one that's really extraordinary by the way that 100 billion figure comes from demographers that estimate starting around 50 000 years ago the rate of population growth and so on how many people have ever lived it's about 100 billion plus the 7.5 billion alive today is the evidence for the resurrection proportional to a hundred billion to one no the evidence for the resurrection is not only not extraordinary it's not even ordinary so the hundred billion people who lived before us have all died not okay so this is uh oh yeah sorry i was picking up here with um philosopher larry shapiro's book who addresses this very nicely in his book the miracle myth why belief in the resurrection and the supernatural is unjustified this is a great book i really learned a lot about how to think like a philosopher which he is evidence for the resurrection is nowhere near as complete or convincing as the evidence on which historians rely to justify belief in other historical events such as the destruction of pope the shapiro's jewish so it's interesting in the first chapter of this book he kind of comes at it like okay you know i'm jewish so this is our book you know the bible and what about this story how come jews don't accept jesus as their messiah and then he kind of takes like a clear-eyed view of well let's analyze what the claims are to see if maybe jews should become christians okay and of course he ends up not doing that because of the way he thinks about it here what about the eyewitnesses to the resurrection people that said they saw jesus you know three days after four days after whatever post-resurrection appearances well shapiro says maybe they were superstitious or credulous and saw what they wanted to see maybe they reported only feeling jesus in spirit and over the decades their testimony was altered to suggest that they saw jesus in the flesh maybe accounts of the resurrection never appeared in the original gospels and were added in later centuries any of these explanations for the gospel descriptions of jesus resurrection are far more likely than the possibility that jesus actually returned to life after being dead for three days or just take something like the miracle of the operation apparition of our lady of fatima in 1917 in fatima portugal three children claimed to have seen a vision of the virgin mary who told one she would return on october 13 to perform a miracle seventy thousand people gathered and saw okay i should say we're told that 70 000 people gathered and saw quote the sun seemed to tear itself from the heavens and come crashing down upon the horrified multitude just when it seemed that the ball of fire would fall upon and destroy them the miracle ceased and the sun resumed its normal place in the sky shining form as peacefully as ever catholics believe this happened including pope john paul ii by the way when i mention that we're told 70 000 people saw it okay this is not a confirmed number again it's like christians say well 500 people saw jesus after the resurrection they saw him reappear no no we have one account that says 500 people saw this one account with a big number is not the same as the big number okay two possibilities the sun really did move about the sky and then start to come crashing down towards the crowd or seventy thousand witnesses or however many there really were were mistaken lied or were misrepresented which one is more likely as impressive as it is that 70 000 people or however many 7 000 whatever witness something this miraculous it's even a greater miracle that the sun would stop that is the earth would stop moving okay this has never happened it's never going to happen therefore everyone because everyone on earth would see it catastrophic consequences adverse stoppage and so on and so forth okay there'd be there'd actually be evidence that that happened from the catastrophe this would cause you know rotating a thousand miles an hour stops things go anywhere uh but much more likely is it never happened of course it's like the miracle pen and tellers bullet catch okay i don't know if you've ever seen this i'm not going to show a clip because i don't have the copyrights to do that uh but just you can google online um okay the one thing we know for sure uh you know when they line up on either side of this stage with the yellow stripe through there um they have volunteers from the audience load the bullets into the guns um the people that are volunteers i i can promise you they're not chills working for penn teller um you know they confirm it's a real gun it's a real bullet then the bullets are fired across the stage pen and teller each catch the other one's bullet as confirmed later by the eyewitnesses who scribbled their initials or a little figure on the bullet shell casein and then the bullet itself and you can see that they've crossed and so on and so forth okay what's more likely right that it really happened that is pen and teller really caught bullets in their teeth fired from 357 magnum handguns or our eyewitness count is mistaken we must perceive the event it's a magic trick etc of course it's a magic trick and nobody thinks that they're actually catching bullets in their teeth right but when we know it's magic then we're i think actually better at critically thinking about this okay so i've been building to this uh principle of ecrete that is from carl sagan who wasn't the first to say this by the way but he said it more succinctly than the original person who was one of the founders of cycop or the what's now called the center for inquiry marcelo chuzi but carl sagan said it more poignantly i think and and more famously in cosmos extraordinary claims require extraordinary evidence it's basically hume's principle proportionality and a little more catchy phrase for the 20th century my favorite example of uh taking that principle and then applying it to the necessity to test your theories uh to determine how much evidence there really is is a thought experiment carl uh presents in his great work the demon haunted world which i uh assigned to this course in which he says um okay just thought experiment i have a dragon in my garage would you like to see it and of course you go yeah i want to see it i'm in a garage here by the way and there's no dragons that i can see but we open the garage door and you look inside and there's you know there's no dragon there's a car there's some bicycles paint cans and fair usual detritus in in a garage and you say well where's the dragon uh well you see this is an invisible dragon oh an invisible dragon yeah it's an invisible dragon well fraggins we know are animals so they give off heat and i have here a heat detector you know one of those things that they use to take your temperature right so that there's these equipment that can do this and um and so you you you whip it out and it's oh no sorry see this dragon is cold-blooded it's it's a cold dragon it doesn't give off heat okay well i have some powder uh here some baking powder so uh some flour so we're going to spread the flower on the floor and when the dragon walks around we'll see his footprints now you see this dragon hovers about three feet above the ground okay so it's an invisible dragon that hovers three feet above the ground right ah but i have some heat detection devices for the fire because we know dragons breathe fire and fire is hot and you get the equipment and your guess your host says no sorry this is cold fire this cold-blooded invisible hovering dragon breeze cold fire that's not measurable okay anyway you see where this is going what's the difference between a invisible hovering cold-blooded cold fire dragon and no dragon at all and of course you can apply this to lots of claims like the existence of god for example if there's no way to test it if there's no way to tell between this hypothesis and this hypothesis the invisible hovering dragon and no dragon at all then the default position is no dragon why is that the default position because in science we know that most of what people think is wrong historically we've mostly gotten it wrong even scientists today when they're spitballing hypotheses to try to explain some phenomena they mostly get it wrong so the null hypothesis that is your hypothesis is not true until you prove otherwise is the default in science you can't go to the fda and say i have a drug that cures cova-19 and expect them to just accept it and approve your drug for sale in the market the burden of proof is on you to prove that you have the drug not on the fda to prove that it isn't true okay as far as i say your extraordinary claim is not true until you prove otherwise so here we say that the burden of proof is on the claimant not the skeptic or scientist to disprove the claim and extraordinary claims require extraordinary evidence what if someone has no evidence at all here we can invoke what i call hitchens dictum another one of my columns in scientific american based on one of the quips from the great hitch what can be asserted without evidence can also be dismissed without evidence okay if you say look i believe bigfoot is real and i say that's nice show me the body i have no body okay well then i dismiss your claim end of conversation then there are negative truths such as the null hypothesis in science that we've been talking about here that the non-existence of something is the truth so here again my example of having a cure for a disease like i use coven 19 here aids before the fda will approve your drug for sale of the public you must provide substantial evidence that your claim is true in the scientific sense that is to reject the null hypothesis that you do not have such a drug or simply when people tell me that bigfoot is real i say show me the body and i'll believe otherwise i remain skeptical so the null hypothesis in this example is that bigfoot does not exist by the way i i have find it very telling that among the thousands of government documents really tens of hundreds of thousands of government documents and files leaked in recent years through wikileaks there's not one mention of the ufo cover-up a fake moon landing or that 911 was an inside job by the bush administration wow that is a really interesting insight here the absence of evidence is evidence of absence because you would expect to be some memo some piece of intel somewhere in there this is the dog that didn't bark in the night from sir arthur conan doyle's story server silver blaze in which sherlock holmes solves the mystery of the prized racehorse kidnapped the midnight visitor was someone the dog knew well because the dog didn't bark two examples of this i think where it may or may not apply so the seti program the search for extraterrestrial intelligence they haven't found anything yet is the absence of evidence evidence of absence that is we now know there's no et's out there no because we've barely started looking just for the last half century or so in just a tiny little sliver of a corner of our galaxy 100 billion stars in our galaxy several hundred billion and several hundred billion up to a trillion galaxies we have a lot of searching to go before we conclude that the absence of evidence is evidence of absence what about god does the absence of evidence here imply this is that is it's evidence of absence of god maybe um i think there's a good argument to be made that if there is a god the universe and the world and life should be a certain way and it surely doesn't seem that way the biggest problem here being the problem of evil um amongst others and uh so victor stanger my late friend and colleague wrote about this where his case against god was a pretty strong one although i generally tend to say it would be difficult to test whether god exists or not because whatever god is doing for your test performing a miracle or whatever this could be done by say far future scientists and engineers or magicians now so through the continuing with our search for truth to the scientific method we aim for objectivity that is the basing of conclusions on external validation and we avoid mysticism or the basing of conclusions on personal insights that lack external validation so here's a quote from the very first professor i ever had in college so wind the clock back to 1972 in my freshman year at glendale college and my philosophy professor richard hardison addressed this in this way this is from my notes which i still have mystical truths by their nature must be solely personal and they can have no possible external validation each has equal claim to truth tea leaf reading and astrology and buddhism each is equally sound or unsound if we judge by the absence of related evidence this is not intended to disparage any one of the fates merely to note the impossibility of verifying their correctness so this is the problem mystic mysticism is based on internal truths that can't even in principle if they can't even in principle be converted into external truth through some kind of test or external validation through corroboration with others then they're forever stuck in the realm of personal truth and that is a different notion entirely than external truths objective truths so the key to reliable knowledge cientia is external validation through experiment or empiricism and especially by corroboration of others so take something like mind-altering drugs like mdma or ecstasy these produce in the part of the participants using them a certain kind of truth uh but is it an external truth or something like ayahuasca or dmt the so-called spirit molecule i've been encouraged to take these so i could better understand what people experience okay i'm tempted uh my wife is not crazy about my uh wanting to do this i haven't done it yet but the problem is is let's say i do it let's say i take ayahuasca and i discovered there's this whole other world that i didn't know about and that no scientist knows about and this this other whatever you want to call it a multi-dimensional place where the colors are incred incredibly rich and the sounds are beautiful and on and on uh and there's these other spirit beings that you can talk to and and whatnot and then if you say well that's nice shermer but prove it and i say well here you take the mda you take the ayahuasca and you'll see it's true that's not the same as a scientific experiment where you conduct the experiment and look at the results and then i can look at your results and somebody else can check your lab your notes your data your analysis and so on this is different than that so and i don't see a way around this to me this will forever be part of internal mystical truths as opposed to external objective truths i'll make here one additional distinction about belief and truths i don't believe in evolution or climate change i accept them as true this multi science doesn't build belief systems in the way that religion and politics does and here i think many political beliefs not all but but most of them are different from scientific beliefs like if i say i believe in a flat tax you believe in a progressive tax and she believes in a regressive tax there's no experiment we're going to determine well which is the true tax there is no true tax it depends on what your goals are and how you want to get to those goals and that depends on a whole bunch of variables and compounds and so on uh so i make that distinction there uh religious truths that jesus lived and was crucified is an empirical historical question i think uh we've addressed that jesus was resurrected from the dead may be a historical question and if so it's the most extraordinary claim ever made okay as we've already addressed but this third one that jesus died for our sins that's not an objective claim that that's a that's a matter of religious belief it's it's pure dogma there's no empirical test we're going to run decide if jesus died for your sins or not okay i'm not even sure it's a good philosophical or theological argument but that's another subject then i want to ask for just a moment are there mysterian mysteries that is mysteries that cannot be answered even in principle okay maybe say take something like the hard problem of consciousness or what it feels like to experience something here i'm not talking about the neural correlates of consciousness where we can measure brain activity in a certain uh neural network when you're thinking about something and say well there's where whatever exists facial recognition or something like this some emotion is involved in that area i'm not talking about that i'm talking about the actual experience of feeling something experiencing it what it feels like to be something and that's called the hard problem i don't see how that could be answered even in principle because it implies that somehow the homunculus in my head can tiptoe over to and get inside your skull to see if the red in your head looks like the red in my head okay so just it's a conceptual problem here it may be one of these mysterious mysteries that can never be answered because either limitations on our thinking or just in our concepts just the language we might hit an epistemological wall there as i say so consciousness may have to be postulated as a brute fact about reality where explanation ends is an epistemological wall an ontological presumption it just is like gravity just is and free will and determinism may depend on how one defines terms like freedom volition and choice now i'm a compatibilist i think we do make uh volitional choices uh because we're part of the causal net of the determined universe so i'm a determinist in the sense that i agree the universe is determined by the laws of nature and so forth but that we're part of that and we're aware of it we're conscious of the factors impinging on us not all of them of course but some of them enough where we can change the future based on the choices we make so that the universe is determined but it's not predetermined and one of the factors in addition to you know quantum phys quantum mechan quantum mechanical randomness and so on is is ourselves we're making choices that alter the future still i i think i throw it in this category simply because um our concepts are so bound with the meaning of the words and you know there's limitations on what we can do with those words i mentioned god before as a way to test it maybe but maybe not it may be a mysterious mystery because as i have argued elsewhere any sufficiently advanced extraterrestrial intelligence is indistinguishable from god so anything you the theist could propose that god could do i can imagine a super advanced extraterrestrial intelligence or a super advanced far future human doing that would make them god so that's not what most people mean by god so then what does that mean okay and finally my favorite mysterious mystery is why is there something rather than nothing well that can't be answered because it's impossible to conceptualize nothing go ahead try it all right so we in the garage here so we take away all the stuff in the garage i have an empty garage but there's still a garage i got to get rid of the garage well there's still the air got to get rid of the air there's still the space time gotta get okay how do you get rid of the space time right more than that not just no matter no energy no space and no time but no mental or platonic concepts no logic or mathematics and no sentient beings asking why there is something rather than nothing because there would be no consciousness no non-physical thing of any kind and thus no god or gods or anything outside of nothing from which to create something not just emptiness forever but not even the existence of emptiness and no forever because there's no time at this point i don't even know what the hell i'm talking about this is truly inconceivable okay back to reality are we living in a post-truth era that is this lecture is about the search for truth there are some people claiming it's not possible that we're living in a post-truth era well i've asked the question it's good to remember uh ian bettager's law of headlines states any headline that ends in a question mark can be answered by the word no okay so this see behind me the cover of skeptic magazine recent issue of skeptic uh with stephen pinker on the cover in which he argued that we are not living in a post-truth era we had originally toyed with the idea of making it a question mark on the cover and then remembered betterage's law of headlines so we didn't want to fall to that as steve starts off with in his article is the statement we are living in a post-truth era true if so it cannot be true that is the evaluation of the proposition is true or false means we're still evaluating propositions based on whether they are true so we are not living in a post-truth era likewise is the statement humans are irrational rational if so it cannot be true if humans were really irrational then who specified the benchmark of rationality against which humans don't measure up and how did they conduct the comparison okay i'm quoting pinker there from his skeptic article so this line of reasoning about reasoning was made most explicitly by the philosopher thomas nagle in his book the last word in which he made the case that truth objectivity and reason are not negotiable because as soon as you're making the case for them or against them you're making a case which means you're implicitly committed to reason nagel calls this a cartesian argument because of descartes cogito ergo sum that is descartes starts to doubt everything he's the ultimate skeptic and then he hit a wall he couldn't doubt the existence of the doubter namely himself so just as the very fact that one might be questioning one's own existence shows that one must exist the very fact that one is examining the question of rationality shows that well one is committed to rationality a corollary is that we don't have faith in reason as nagel puts it this is one thought too many we don't believe in reason we use reason and people are more reasonable than we think so for example i've written elsewhere about the research by andrew guess brandon nyan and jason reiffler conducted a quantitative analysis of the role of fake news in the 2016 election and found that fake news took up far less than one percent by the way these researchers originally were doing uh research on uh the backfire effect that is if you present people with evidence against one of their beliefs they'll double down on the belief okay turns out this these experiments have not been replicated and there's lots of examples to doubt that this is one of them first of all that there wasn't all that much fake news and that it had next to no effect on the election so for example as only people who already hated hillary would believe that she was running a child sex ring out of a washington dc pizzeria okay so it's not like that crazy conspiracy theory spread and trump won no it had no effect on the election and it's often said that you can't reason people out of beliefs that they didn't reason themselves into in the first place that's not true i get letters every day from people who change their minds after reading something i wrote and nian and rifler in their study showed that evidence can change people's minds even on highly politicized issues if it's presented in a clear and compelling format most notably graphs here i'm thinking of climate change for example but there's one other factor you have to take out of the equation some particular belief that people are not going to give up like their religious beliefs or their political party almost nobody changes those so if you make your factual claim linked to them having to give up that belief they're less likely to do that because beliefs can also be signals of group loyalty so things like climate change evolution capitalism trade agreements most people don't know much about them but taking a position is a sign of loyalty it's a kind of virtue signaling i don't know much about climate change climate science i've tried to read some of the papers they're very technical i trust the mechanisms of science that the competitive enterprise of climate scientists say weeds out the bad ideas and the good ideas end up floating to the surface that we consume as consumers of science as dan kahan says science denial is not correlated with scientific illiteracy that is climate believers believers in climate change they don't know anything more about climate science than climate deniers so what does predict it it's political orientation as we know the left is skeptical of gmos vaccines and the right is skeptical of climate change so the number one predictor of somebody's position on these scientific issues is not their knowledge of the science it's something else usually their political or religious beliefs so we need to decouple science from politics like climate change and associated with al gore because of his film or as i like to say if you give christians a choice between darwin and jesus they're not taking darwin in any case why would they because darwin didn't die for your sins okay so but you have to take that off the table you just say look you can keep jesus the souls god the whole thing i'm just talking about a particular science here here's the evidence for it you can see it if you like is god's way of creating living organisms something like that i talk about this at length in my lecture on creationism then there are rational irrationalities that is there's times when we don't want to know the truth exactly so like when nixon uh floated his idea about bringing about the end of the vietnam war that that he was just crazy enough to use nukes he let that leak to our opponents the north koreans and the chinese this became known as the madman theory like he's rationally irrational at least on the surface of it some people have suggested that about trump although i'm not sure he's that rational enough to rationally be rationally irrational religious fervor and terrorism they may just be crazy enough to fly a plane into a building yes so the problem with mutual assured destruction as a strategic cold war strategy for nuclear weapons is that it's based on the rational actor theory it only works when you presume the other guy doesn't want to die uh a doomsday machine only works if both sides know about it okay so here i'm going to show a little video clip from uh my one of my favorite films uh dr strangelove uh in which um they're in the war room here and and they discover through the the russian ambassador that the russians had this doomsday machine but nobody knew about it there's no point in having a doomsday machine unless everybody knows about it that's the idea so um here's that little clip let's see if this play's okay so that within 10 months the surface of the earth will be as dead as the moon is ridiculous our study showed even the worst fallout is down to a safe level after two weeks you've obviously never heard of cabal thorium g well what about it about thorium g has a radioactive half-life of 93 years if you take say 50 h bombs in 100 megaton range and jacket them with cabal thorium g when they are exploded they will produce a doomsday shroud a legal cloud of radioactivity which will encircle the earth for 93 years what a load of commie bull i mean after all afraid i don't understand something alexa is the premier threatening to explode this if our planes carry out their attack no sir it is not a thing a saiyan man would do the doomsday machine is designed to trigger itself automatically but surely you can disarm it somehow no it is designed to explode if any attempt is ever made to untrigger it automatically that's an obvious coming trick mr president we're wasting valuables look at me i'm getting ready to clobber us well this is absolute madness ambassador why should you build such a thing there were those of us who fought against it but in the end we could not keep up with the expense involved in the arms race the space race and the peace race and at the same time our people grumbled for more nylons and washing machines our doomsday scheme cost us just a small fraction of what we've been spending on defense in a single year but the deciding factor was when we learned that your country was working along similar lines and we were afraid of a doomsday gap this is preposterous i've never approved of anything like that our source was the new york times dr strangelove do we have anything like that in the works a moment please mr president under the authority granted me as director of weapons research and development i commissioned last year a study of this project by the blend corporation based on the findings of the report my conclusion was that this idea was not a practical deterrent for reasons which at this moment must be all too obvious then you mean it is possible for them to have built such a thing mr presidency technology required is easily within the means of even the smallest nuclear power it requires only the hill to do so but how is it possible for this thing to be triggered automatically and at the same time impossible to untrigger mr president it is not only possible it is essential that is the whole idea of this machine you know deterrence is the art of producing in the mind of the enemy the fear to attack and so because of the automated and irrevocable decision-making process which rules out human meddling the doomsday machine is terrifying yes simple to understand and completely credible and convincing gee i wish we had one of them doomsday machines dainty but this is fantastic strange love how can it be triggered automatically well it's remarkably simple to do that when you merely wish the berry bombs there's no limit to the size after that they are connected to a gigantic complex of computers now then a specific and clearly defined set of circumstances under which the bombs are to be exploded is programmed into a tape memory bank a single roll of shape can store all the information changed when you became a is that the whole point of the doomsday machine is lost if you keep it the secret why didn't you tell the world eh it was to be announced at the party congress on monday as you know the premier love surprises so speaking of nuclear weapons let me continue here and introduce you to the man who saved the world this is a poster from a recent documentary on colonel stanislav petrov who is now called the man who changed the world on september 26 1983 three weeks after soviet military shot down korean airlines flight 007 petrov was the duty officer at the command center for the oco nuclear early warning system when the system reported that five missiles had been launched from the united states petrov judged the reports to be a false alarm and his decision to disobey orders against soviet military protocol is credited with having prevented an erroneous retaliatory nuclear attack on the united states and his nato allies that would have resulted in large-scale nuclear war and the deaths of hundreds of millions of people and turns out petrov was right investigation later determined that the false alarm had been created by a rare alignment of sunlight on high altitude clouds above north dakota and the highly elliptical orbits of satellites later corrected by cross-referencing a geostationary satellite here is the trailer for that film it's quite good most of you might remember when the cold war was at its height the soviet union just shot down a korean jet we live in a world in which the great powers have poised and aimed at each other nuclear weapons that can in a matter of minutes arrive in each other's country and destroy virtually the civilized world we live in foreign it's up to him to tell his leadership to launch a counter-attack which probably would wipe down half of our population museum [Music] what a privilege to meet you the man who saved the world i'm not a hero i was just in the right place at the right time well yes i think i think that's right because we're not uh sure how we know that he knew it was a good guess in any case but this is a problem in signal detection so i'm going to introduce again i introduce this in my cognitive biases lecture the two by two matrix of how we determine whether something is true or not by eliminating other possibilities and i'll come back to this uh in just a moment but this this is my favorite example of this in which um i was tasked with um being the talking head on a documentary about cursed horror films that is horror films in which bad things happen to the actors and people affiliated with the film either during the filming or or or shortly after and so here's the little clip from that in which i explain this two by two matrix as a uh a tool on in in determining whether something is true or not i'd like you to think about putting those films that are cursed in a box and we're gonna put this box right here and then we're going to draw a square around it in which we have three other boxes so in this box number one we have cursed horror films poltergeist and the crow and the exorcist and so on now what i want you to think about is the second box over here which are cursed non-horror films superman you know i mean christopher reeves fell off a horse broke his neck and apocalypse now you know martin sheen has a heart attack and all these weird things that happen okay why aren't we talking about that cell because they're not horror films in this box down here i want you to think about non-cursed horror films like the shiny come and play with us danny this is one of the scariest films ever made [Music] no curses or more recently it or get out why don't we notice those and then the fourth category of course is non-cursed non-horror films pick any of them citizen kane casablanca you know people had long careers after that nothing weird happened so you have to keep in mind all four categories and remind yourself look i'm only focusing on this one but all the other ones put it into context and when you see the bigger picture you realize okay there's actually nothing to be explained i'd like you to think of so here's that two by two cell that we're going to use for looking at other issues here as we wrap up this lecture so in cell number one you have horror films that are cursed like poltergeist and exorcist the omen crow twilight zone the movie somebody's actually decapitated by a helicopter in the filming of twilight zone the movie then there's horror films that are not cursed super scary ones like it the ring the sixth sense the shining and then non-horror films cursed like superband wizard of oz rebel without a cause apocalypse now and then non-or non-cursed films like the godfather star wars casablanca citizen kane so in other words by focusing on this one cell here that to the exclusion of the others we're getting a distortion about a a false correlation a correlation between curses and horror films that doesn't really exist it doesn't exist because of all the other exceptions um here so there's really nothing that needs explaining i hated to tell this to the filmmakers but to their credit uh they included my explanation so that i really appreciated that so let's go back to uh stanislav petrov and his his issue as you saw in that little trailer he had 15 minutes that's right that's how it works you have about 15 minutes to make a decision that the signal you're getting on your radar screen is at missiles because there's certain protocols that we have for example launch on warning that is to say it's a little risky to wait to see if the missiles actually strike before you launch a counter-strike because what if they knock out all your missiles and well of course that's why we have the triad we have bombers and we have submarines and missiles land-based missiles so but the idea is that uh you can't wait 15 minutes because if they take out our missiles then we can't retaliate so we have to retaliate just a warning well is the warning a true warning or not well here's our two by two matrix in the upper left we have real missiles um and we signal yes they're real and we launch a retaliatory strike so um you know so that's a that's a hit well okay so i say no damage the idea is that we so-called missile defense system we we knock down their missiles this probably isn't possible in fact i know it's not possible and then in the other cell you have real missiles and and you decide um that they're not and then that therefore that's a miss and then your cities are destroyed or the bottom left cell it's a false signal and excuse me you decide it's a real they're really missiles and that's a false alarm so you've wasted a response in which case bad for the enemy because we've launched our missiles to them and of course they're going to retaliate so that's going to actually be a disaster for us or that the the missiles are really a fault signal and you reject that a correct rejection so that's at no cost but we can apply this to lots of other things in life which is where i'm kind of wrapping it up here why this lecture is important that is to say determining the cause of things determining whether something is true or not trying to figure out what the hell is going on applies in everything we do so let's say you get a blob on your x-ray is it cancer or no well if it's really cancer and you decide it is really cancer and you get the treatment and the surgery and the radiation and the chemo and so on that's a correct hit and you hopefully saved your life excuse me in the upper right you you you really do have cancer but you decide now the blob is a false alarm and you miss that you could die from that cancer or the signal is false you don't have cancer and you decide that you do and you go through the treatment that's a false alarm needless surgery chemo and so forth and then finally there is no cancer and you correctly reject it no cost criminal justice system is based on this okay nobody is omniscient including the judges and juries especially so we have a real criminal and we determine that he's guilty that's a hit and justice has been served but if it's a real criminal and we let him go that's a miss so there's one form of injustice or the person really didn't do it and we decide that he's guilty that's a false alarm but that's an injustice because you've falsely imprisoned somebody and of course the person didn't do it and they were found to be not guilty that's a correct rejection that's a form of justice although there is a cost in the trial and the stress on the falsely accused person so that's a problem of criminal signal detection or just think about what we're going through right now with covet 19 that's a signal detection problem that is should we socially isolate or should we continue on as business as usual or something in between well upper left cell social social isolation and it turned out that was the decision we made it turned out that covet 19 was catastrophic so that was good to socially isolate that's a hit we saved a lot of lives or but on the upper right not so good right we continue with business as usual covet 19 turns out to be catastrophic that's a miss that's a type 2 error of false negative and many millions die or bottom left we socially isolate and cover 19 was moderate so that's a false positive a type 1 error and that hurts the economy probably what happened but we don't still don't know for sure the time i'm recording this in june of 2020 or on the bottom right we continue on business as usual and it turns out that coven 19 wasn't so bad that's a correct rejection and the economy is not destroyed and finally even marriage right i call this a spousal or spouse signal detection well you know when you marry somebody hopefully it's the right person but of course nobody knows for sure no one's omniscient and so there's always a risk that you've made the wrong decision so in the upper left corner you made the right decision this is actually the best person for you or the right person for you at this time and you decide to marry them that's a hit and you have a happy marriage in the upper right the the spouse this person you were going to marry what was the right person for you and you declined to marry them that's a miss so you try again and no i don't believe that there's only one right person for you so we'll just put that out there you can always find somebody else but anyway in terms of how this works and bottom left cell the person was not the right person for you and you do marry them that's a false alarm and they could end up in an unhappy marriage and that is one reason why we have such a high divorce rate people have poor reasoning abilities about spousal signal detection and in the bottom right this was not the right person for you you didn't marry them that's a correct rejection and you try again now if that seems kind of cold this spouse signal detection you mean to tell me love has evidence has something to do with love yes so i'll close out with a little joke from didn't mention do you know what they call love without evidence stalking okay evidence is all important for determining what the hell is going on in all areas of life that is we want to understand causality we want to know what's true thanks for listening you

Channel: Skeptic

Views: 4,659

Rating: 4.8651686 out of 5

Keywords: Michael Shermer, skepticism, truth, subjective/objective truths, theory of causality, correlation and causation, principle of proportionality, miracles, post-truth, rational irrationalities, Bayesian reasoning, love

Id: 1Fn0uTFVxlY

Length: 84min 32sec (5072 seconds)

Published: Fri Jun 26 2020