Chapter 7 Let us take a step back and ask a fundamental question: why should you believe that the things I am telling you are true? After all, I started this book with a story about how someone lied to me. Maybe that was an ironic warning that I am not trustworthy? How can you be sure? In particular, why should you believe me about the *history*? Why should you believe that, say, Isaac Newton discovered the laws of gravity, or that Albert Einstein's work on Brownian motion is what convinced scientists that atoms exist? After all, I'm not a historian. All the information about the history of science that I've includes in the previous chapters comes pretty much entirely from Wikipedia, and why should you believe Wikipedia? One possible answer to this is that *everyone just knows* that Wikipedia is a more-or-less reliable source of information. But that is a very bad reason to believe what you read in Wikipedia. What "everyone knows" depends almost entirely on what social circles you move in. If, say, you have a lot of religious friends, then "everyone knows" that God exists. If, on the other hand, you hang out with atheists, then "everyone knows" that He doesn't. Obviously both groups can't be right. If you wanted to, you could actually verify Newton's laws for yourself. You can buy a very good telescope for relatively little money nowadays. If you are feeling particularly ambitious you can make one yourself. That plus a little mathematical elbow grease will allow you to personally verify that gravity works the way Newton says it does. Chemistry and thermodynamics are a little further out of reach of the contemporary amateur because noodling around with them is potentially dangerous and society is a little less carefree than it used to be. But if you really wanted to, you could personally verify many of the claims made in the previous two chapters. But that would be an awful lot of work. And even if you were willing to undertake it, you would eventually hit a limit of what you could personally verify. The body of scientific knowledge is vast and growing rapidly (to say nothing of the cost of the equipment needed to do experiments at the leading edge). Trying to reproduce even a tiny fraction of it for yourself could easily consume your entire life. That's not necessarily a bad way to spend your time, but existence offers other joys besides hanging out in a lab. So what to do? Are you really forced to choose between spending all your time verifying everything for yourself and being a mark for charlatans? Happily the answer to this question is no, there is a better way. And at this point it should not come as a huge surprise to you to learn that this better way is to apply the scientific method to this very problem! In other words, the answer is to try to come up with the best explanation to explain your observations, and in particular, your observation that you are reading these words, and that Wikipedia and other sources say what they say. There is an obvious explanation to account for the observation that you are reading these words: someone wrote them. But that is not the only possible explanation. It is possible, for example, that these words were written by an AI. In fact, by the time you read this, that will almost certainly be a *plausible* explanation. I am writing these words on December 26, 2022, and there has recently (like earlier this year) been a breakthrough in AI technology that makes it possible for AI, for the first time, to write long coherent passages with complex lines of reasoning. The further into the future you go, the more advanced this technology will get (assuming civilization doesn't collapse, but that's another story) and the harder it will become to tell whether any particular passage was written by a person or a machine. Does this matter? Yes, it does, because the *source* of the information can tell you a lot about its reliability. If a camp counselor tells you that there is a danger of being eaten by carnivorous automobiles the most likely explanation of that (i.e. the fact that the counselor is telling you this) is very different than if, say, a national park ranger tells you that there is a danger of being eaten by bears. Humans are very complex creatures and our communications are shot-through with context and nuance. We say all kinds of things that aren't true for all kinds of reasons ranging from sinister to innocent to outright constructive: there is an entire genre of human communications called "fiction" where we say things that aren't true in order to entertain ourselves! So we now have at least three possible explanations to account for the existence of these words: 1. They were written by an AI 2. They were written by a human, and that human is telling the truth 3. They were written by a human, and that human is not telling the truth We can further refine hypothesis #3: 3a. They were written by a human who believed in good faith that he was telling the truth, but he was wrong 3b. They were written by a human who knew full well that what he was writing was not the truth And even further: 3c. They were written by a human who was trying to write fiction for entertainment 3d. They were written by a human in a deliberate attempt to deceive you That last one might seem like a bit of a stretch here, but it's not completely out of the question. I think it's actually the most likely explanation to account for my camp counselor telling me about car-eating Cadillacs at summer camp. With the benefit of hindsight it seems pretty clear that he knew perfectly well that he was lying to me. Why would he do that? I can think of two possible explanations: 1. He was trying to teach me a lesson, namely, that people sometimes lie and that I cannot assume that everything I am told is the truth 2. He was an asshole who got off on the fact that young children would believe even the most outrageous lies Which of these is true? I have no idea, and it is now much too late to ever know for certain. But it doesn't really matter. I don't have to know *why* he was lying to me to be very certain *that* he was lying to me. The mere existence of a plausible explanation makes me confident in my conclusion even if my explanation is not actually correct! The existence of multiple plausible explanations doesn't change that. The flip side of the fact that people sometimes lie is that they do not always lie. Very often -- in fact, most of the time -- people tell the truth, or at least what they believe in good faith to be the truth. And most of the time when people do not tell the truth they do it in a context where it doesn't really matter (e.g. Saying "Fine, thanks" in response to "How are you?" even if they are not fine) or where it is clear that they do not intend for you to take what they are saying at face value (e.g. "Santa brought the kids presents on Christmas") or by sending some kind of signal to indicate that what they are about to say is not to be taken as the literal truth (e.g. "I heard this great joke...") Ironically, the fact that people tell the truth (or at least what they believe in good faith to be the truth) most of the time is exactly why people often believe lies. If you assume that anything anyone tells you is true, you will be right most of the time. Unfortunately, even a single mistake in this regard made under inopportune circumstances can have severe negative consequences, so being able to tell when someone is not telling the truth is a useful skill to cultivate. It can quite literally save your life to be able to tell when, for example, "This is perfectly safe" isn't true. Sadly, learning to detect untruths is not an easy skill to learn. I can't just give you a formula, at least not beyond the one I have already given you, namely, the scientific method: find the best explanation for everything you observe and act *as if* that explanation is the truth. I emphasize the "as if" here because the best explanation is not necessarily the actual truth. In fact, it usually isn't the truth, at least, not the whole truth. Scientific explanations are always subject to revision and refinement as new data and better ideas become available. All scientific knowledge is at all times tentative. With that in mind let us return to the opening question of this chapter: why should you believe that the things I am telling you are true? The answer is: you shouldn't! You should be skeptical. I might be lying to you. Or I might be telling you things that I believe in good faith to be true, but I'm just wrong. This whole "scientific method" thing might be totally bogus. How do you decide? The key is to take note of another key phrase in my description of the scientific method: find the best explanation for *everything you* observe. And that starts with your everyday experiences. If you are reading this in the not-too-distant future then your everyday experience includes things like computers and cell phones. How did those things come to be? Well, they were *made* by other humans, and if you do enough homework you can learn exactly how they were made, even to the point where you can make something like a computer or a cell phone yourself. (Making an actual modern computer or cell phone is much too complicated for a single human to be able to pull it off without a lot of help.) (If you are reading this in the very distant future then either your everyday experience includes technology that I cannot even begin to imagine, or civilization has collapsed and you may never have heard of a computer or a cell phone. I'll address that later.) Not just anyone can make a computer or a cell phone. You need a fair bit of specialized knowledge. The details of that knowledge don't matter all that much for the moment. What matters is that, if you dig in, you will find that this knowledge contains a few core tenets, which I am going to refer to as the "laws of physics". This phrase, "laws of physics", can refer to two different things. It can refer to the *actual laws* that govern the behavior of our universe (which presupposes that our universe is actually governed by laws, which is not necessarily the case), or it can refer to *our understanding* of those (alleged) laws. The latter is not necessarily the same as the former, even assuming that the former even exists. But I am now going to present you with an *argument* that 1) the behavior of the universe actually is governed, at least to a certain extent, by laws and that 2) our understanding of those laws is a pretty good approximation to what those laws actually are. I submit that *this is the best explanation for the existence of computers and cell phones*. Why is this the best explanation? Because there literally is no other possibility that is even remotely plausible. Any alternative explanation that you could offer has to explain not only the existence of computers and cell phones, but the existence of a vast body of *written knowledge* about how computers and cell phones are made and how they work. And this written knowledge contains core elements that are every bit as uncontroversial as the very existence of computers and cells phones. Indeed, we can push this argument one level deeper and say that the *actual existence* of computers and cell phones it the best explanation for the observation that you can see and interact with computers and cell phones, and with people who profess to be able to see and interact with computers and cell phones. This is not the only possible explanation -- maybe everyone is suffering from some kind of collective delusion. Or maybe aliens have our planet in the grip of a mind-control ray. If I have to persuade you that these explanations are unlikely, then you should probably stop reading now. Every non-mentally-ill human has the common experience of interacting with -- indeed, of actually *being* -- a material object. Furthermore, with a very few unfortunate exceptions, every human has the common experience of interacting with *other humans*, which is to say, with other material objects that exhibit very similar physical appearance and behavior as themselves, and with which they can *communicate*, and with which they, for the most part, agree about certain basic facts, like the existence of computers and cell phones and other material objects. The best explanation for all those observations is that these material objects that everyone professes to perceive in the same way *actually exist*. Now, I am going to skip ahead about a hundred chapters and tell you that this is actually *not* the correct answer. There is a branch of physics called "quantum mechanics" which provides conclusive evidence that the actual existence of material objects is *not* the best explanation for our shared perception of their existence. But this has only come to light very, very recently (like in the last 50-100 years) and for the time being you can totally ignore this. So: let us proceed on the assumption, a "working hypothesis" as they say in the trade, that material objects actually do exist, and that their nature is more or less as we perceive them to be: they exist at particular places at particular times. They have *identity*, so it makes sense to say that a particular thing moved from here to there, and that after it moved it was still the "same thing". We can condense about two thousand years of human intellectual endeavor down to the pithy phrase: our universe consists of things, which are are made of matter, which is made of atoms. Oh, and there's also this weird thing called "light", which allows us to "see". We'll get to that. There are also a couple of other weird things like neutrinos and muons and whatnot, but you can safely ignore those unless you want to become a nuclear physicist. Atoms and light are literally all there is that has any bearing on your day-to-day existence here on earth. All of these things might not be true. Indeed, I have already told you that they are *not* true. But absent some very compelling evidence (and there will be some) and a damned good argument (and there will be one), anyone who doesn't accept this could rightfully be written off as mentally ill, or at least incorrigibly obstreperous. The term of art for the laws of physics based on the assumption that material objects actually exist is *classical mechanics*. These are the laws of physics originally discovered by Isaac Newton to explain the motions of planets, but which turn out to explain a vast range of phenomena here on earth as well. I'm not going to go into too much detail about this. If you really want to know there are a ton of books already written about it. But there is one piece of classical mechanics that matters more than anything else for day-to-day life, and that will be the subject of the next chapter. Homework: I haven't totally answered the question I posed at the beginning of this chapter. I've given you a compelling reason to believe that the laws of physics are true, but not yet a compelling reason to believe the stories I've told you about how they were discovered. Is there a compelling reason to believe those stories? What is it?