The Meaning of It All: Thoughts of a Citizen-Scientist - Softcover

Feynman, Richard

Softcover

ISBN 10: 0465023940 ISBN 13: 9780465023943

Publisher: Basic Books, 2005

Synopsis

Many appreciate Richard P. Feynman's contributions to twentieth-century physics, but few realize how engaged he was with the world around him-how deeply and thoughtfully he considered the religious, political, and social issues of his day. Now, a wonderful book-based on a previously unpublished, three-part public lecture he gave at the University of Washington in 1963-shows us this other side of Feynman, as he expounds on the inherent conflict between science and religion, people's distrust of politicians, and our universal fascination with flying saucers, faith healing, and mental telepathy. Here we see Feynman in top form: nearly bursting into a Navajo war chant, then pressing for an overhaul of the English language (if you want to know why Johnny can't read, just look at the spelling of "friend") and, finally, ruminating on the death of his first wife from tuberculosis. This is quintessential Feynman-reflective, amusing, and ever enlightening.

About this title

About the Author

Richard P. Feynman was raised in Far Rockaway, New York, and received his Ph.D. from Princeton. He held professorships at both Cornell and the California Institute of Technology. In 1965 he received the Nobel Prize for his work on quantum electrodynamics. He died in 1988.

Excerpt. © Reprinted by permission. All rights reserved.

The Meaning of It All

Thoughts of a Citizen-ScientistBy Richard Phillips Feynman

Basic Books

Copyright © 2005 Richard Phillips Feynman
All right reserved.
ISBN: 9780465023943

Chapter One

The Uncertainty of Science

I WANT TO ADDRESS myself directly to the impact ofscience on man's ideas in other fields, a subject Mr. JohnDanz particularly wanted to be discussed. In the first of theselectures I will talk about the nature of science andemphasize particularly the existence of doubt and uncertainty.In the second lecture I will discuss the impact of scientificviews on political questions, in particular the question ofnational enemies, and on religious questions. And in the thirdlecture I will describe how society looks to me--I could sayhow society looks to a scientific man, but it is only how itlooks to me--and what future scientific discoveries mayproduce in terms of social problems.

    What do I know of religion and politics? Several friendsin the physics departments here and in other places laughedand said, "I'd like to come and hear what you have to say. Inever knew you were interested very much in those things."They mean, of course, I am interested, but I would not dareto talk about them.

    In talking about the impact of ideas in one field on ideasin another field, one is always apt to make a fool of oneself.In these days of specialization there are too few people whohave such a deep understanding of two departments of ourknowledge that they do not make fools of themselves in oneor the other.

    The ideas I wish to describe are old ideas. There ispractically nothing that I am going to say tonight that couldnot easily have been said by philosophers of the seventeenthcentury. Why repeat all this? Because there are newgenerations born every day. Because there are great ideasdeveloped in the history of man, and these ideas do not lastunless they are passed purposely and clearly fromgeneration to generation.

    Many old ideas have become such common knowledgethat it is not necessary to talk about or explain them again.But the ideas associated with the problems of thedevelopment of science, as far as I can see by lookingaround me, are not of the kind that everyone appreciates. Itis true that a large number of people do appreciate them.And in a university particularly most people appreciate them,and you may be the wrong audience for me.

    New in this difficult business of talking about theimpact of the ideas of one field on those of another, I shallstart at the end that I know. I do know about science. Iknow its ideas and its methods, its attitudes towardknowledge, the sources of its progress, its mental discipline.And therefore, in this first lecture, I shall talk about thescience that I know, and I shall leave the more ridiculous ofmy statements for the next two lectures, at which, I assume,the general law is that the audiences will be smaller.

    What is science? The word is usually used to mean oneof three things, or a mixture of them. I do not think we needto be precise--it is not always a good idea to betoo precise. Science means, sometimes, a special method offinding things out. Sometimes it means the body ofknowledge arising from the things found out. It may alsomean the new things you can do when you have foundsomething out, or the actual doing of new things. This lastfield is usually called technology--but if you look at thescience section in Time magazine you will find it coversabout 50 percent what new things are found out and about50 percent what new things can be and are being done. Andso the popular definition of science is partly technology, too.

    I want to discuss these three aspects of science inreverse order. I will begin with the new things that you cando--that is, with technology. The most obvious characteristicof science is its application, the fact that as a consequenceof science one has a power to do things. And the effect thispower has had need hardly be mentioned. The wholeindustrial revolution would almost have been impossiblewithout the development of science. The possibilities todayof producing quantities of food adequate for such a largepopulation, of controlling sickness--the very fact that therecan be free men without the necessity of slavery for fullproduction--are very likely the result of the development ofscientific means of production.

    Now this power to do things carries with it noinstructions on how to use it, whether to use it for good orfor evil. The product of this power is either good orevil, depending on how it is used. We like improvedproduction, but we have problems with automation. We arehappy with the development of medicine, and then we worryabout the number of births and the fact that no one dies fromthe diseases we have eliminated. Or else, with the sameknowledge of bacteria, we have hidden laboratories in whichmen are working as hard as they can to develop bacteria forwhich no one else will be able to find a cure. We are happywith the development of air transportation and are impressedby the great airplanes, but we are aware also of the severehorrors of air war. We are pleased by the ability tocommunicate between nations, and then we worry about thefact that we can be snooped upon so easily. We are excitedby the fact that space can now be entered; well, we willundoubtedly have a difficulty there, too. The most famous ofall these imbalances is the development of nuclear energyand its obvious problems.

    Is science of any value?

    I think a power to do something is of value. Whetherthe result is a good thing or a bad thing depends on how it isused, but the power is a value.

    Once in Hawaii I was taken to see a Buddhist temple.In the temple a man said, "I am going to tell you somethingthat you will never forget." And then he said, "To every manis given the key to the gates of heaven. The same key opensthe gates of hell."

    And so it is with science. In a way it is a key to thegates of heaven, and the same key opens the gates of hell,and we do not have any instructions as to which is whichgate. Shall we throw away the key and never have a way toenter the gates of heaven? Or shall we struggle with theproblem of which is the best way to use the key? That is, ofcourse, a very serious question, but I think that we cannotdeny the value of the key to the gates of heaven.

    All the major problems of the relations between societyand science lie in this same area. When the scientist is toldthat he must be more responsible for his effects on society, itis the applications of science that are referred to. If youwork to develop nuclear energy you must realize also that itcan be used harmfully. Therefore, you would expect that, ina discussion of this kind by a scientist, this would be the mostimportant topic. But I will not talk about it further. I thinkthat to say these are scientific problems is an exaggeration.They are far more humanitarian problems. The fact that howto work the power is clear, but how to control it is not, issomething not so scientific and is not something that thescientist knows so much about.

    Let me illustrate why I do not want to talk about this.Some time ago, in about 1949 or 1950, I went to Brazil toteach physics. There was a Point Four program in thosedays, which was very exciting--everyone was going to helpthe underdeveloped countries. What they needed, of course,was technical know-how.

    In Brazil I lived in the city of Rio. In Rio there arehills on which are homes made with broken pieces of woodfrom old signs and so forth. The people are extremely poor.They have no sewers and no water. In order to get waterthey carry old gasoline cans on their heads down the hills.They go to a place where a new building is being built,because there they have water for mixing cement. Thepeople fill their cans with water and carry them up the hills.And later you see the water dripping down the hill in dirtysewage. It is a pitiful thing.

    Right next to these hills are the exciting buildings of theCopacabana beach, beautiful apartments, and so on.

    And I said to my friends in the Point Four program, "Isthis a problem of technical know-how? They don't knowhow to put a pipe up the hill? They don't know how to put apipe to the top of the hill so that the people can at least walkuphill with the empty cans and downhill with the full cans?"

    So it is not a problem of technical know-how. Certainlynot, because in the neighboring apartment buildings there arepipes, and there are pumps. We realize that now. Now wethink it is a problem of economic assistance, and we do notknow whether that really works or not. And the question ofhow much it costs to put a pipe and a pump to the top ofeach of the hills is not one that seems worth discussing, tome.

    Although we do not know how to solve the problem, Iwould like to point out that we tried two things, technicalknow-how and economic assistance. We arediscouraged with them both, and we are trying somethingelse. As you will see later, I find this encouraging. I thinkthat to keep trying new solutions is the way to do everything.

    Those, then are the practical aspects of science, thenew things that you can do. They are so obvious that we donot need to speak about them further.

    The next aspect of science is its contents, the thingsthat have been found out. This is the yield. This is the gold.This is the excitement, the pay you get for all the disciplinedthinking and hard work. The work is not done for the sake ofan application. It is done for the excitement of what is foundout. Perhaps most of you know this. But to those of you whodo not know it, it is almost impossible for me to convey in alecture this important aspect, this exciting part, the realreason for science. And without understanding this you missthe whole point. You cannot understand science and itsrelation to anything else unless you understand andappreciate the great adventure of our time. You do notlive in your time unless you understand that this is atremendous adventure and a wild and exciting thing.

    Do you think it is dull? It isn't. It is most difficult toconvey, but perhaps I can give some idea of it. Let me startanywhere, with any idea.

    For instance, the ancients believed that the earth wasthe back of an elephant that stood on a tortoise that swam ina bottomless sea. Of course, what held up thesea was another question. They did not know the answer.

    The belief of the ancients was the result of imagination.It was a poetic and beautiful idea. Look at the way we see ittoday. Is that a dull idea? The world is a spinning ball, andpeople are held on it on all sides, some of them upside down.And we turn like a spit in front of a great fire. We whirlaround the sun. That is more romantic, more exciting. Andwhat holds us? The force of gravitation, which is not only athing of the earth but is the thing that makes the earth roundin the first place, holds the sun together and keeps us runningaround the sun in our perpetual attempt to stay away. Thisgravity holds its sway not only on the stars but between thestars; it holds them in the great galaxies for miles and milesin all directions.

    This universe has been described by many, but it justgoes on, with its edge as unknown as the bottom of thebottomless sea of the other idea--just as mysterious, just asawe-inspiring, and just as incomplete as the poetic picturesthat came before.

    But see that the imagination of nature is far, far greaterthan the imagination of man. No one who did not have someinkling of this through observations could ever have imaginedsuch a marvel as nature is.

    Or the earth and time. Have you read anywhere, byany poet, anything about time that compares with real time,with the long, slow process of evolution? Nay,I went too quickly. First, there was the earth withoutanything alive on it. For billions of years this ball wasspinning with its sunsets and its waves and the sea and thenoises, and there was no thing alive to appreciate it. Can youconceive, can you appreciate or fit into your ideas what canbe the meaning of a world without a living thing on it? Weare so used to looking at the world from the point of view ofliving things that we cannot understand what it means not tobe alive, and yet most of the time the world had nothing aliveon it. And in most places in the universe today there probablyis nothing alive.

    Or life itself. The internal machinery of life, thechemistry of the parts, is something beautiful. And it turnsout that all life is interconnected with all other life. There is apart of chlorophyll, an important chemical in the oxygenprocesses in plants, that has a kind of square pattern; it is arather pretty ring called a benzine ring. And far removedfrom the plants are animals like ourselves, and in our oxygen-containingsystems, in the blood, the hemoglobin, there arethe same interesting and peculiar square rings. There is ironin the center of them instead of magnesium, so they are notgreen but red, but they are the same rings.

    The proteins of bacteria and the proteins of humans arethe same. In fact it has recently been found that the protein-makingmachinery in the bacteria can be given orders frommaterial from the red cells to produce redcell proteins. So close is life to life. The universality of thedeep chemistry of living things is indeed a fantastic andbeautiful thing. And all the time we human beings havebeen too proud even to recognize our kinship with theanimals.

    Or there are the atoms. Beautiful--mile upon mile ofone ball after another ball in some repeating pattern in acrystal. Things that look quiet and still, like a glass of waterwith a covered top that has been sitting for several days, areactive all the time; the atoms are leaving the surface,bouncing around inside, and coming back. What looks still toour crude eyes is a wild and dynamic dance.

    And, again, it has been discovered that all the world ismade of the same atoms, that the stars are of the same stuffas ourselves. It then becomes a question of where our stuffcame from. Not just where did life come from, or where didthe earth come from, but where did the stuff of life and ofthe earth come from? It looks as if it was belched fromsome exploding star, much as some of the stars areexploding now. So this piece of dirt waits four and a halfbillion years and evolves and changes, and now a strangecreature stands here with instruments and talks to thestrange creatures in the audience. What a wonderful world!

    Or take the physiology of human beings. It makes nodifference what I talk about. If you look closely enough atanything, you will see that there is nothingmore exciting than the truth, the pay dirt of the scientist,discovered by his painstaking efforts.

    In physiology you can think of pumping blood, theexciting movements of a girl jumping a jump rope. Whatgoes on inside? The blood pumping, the interconnectingnerves--how quickly the influences of the muscle nerves feedright back to the brain to say, "Now we have touched theground, now increase the tension so I do not hurt the heels."And as the girl dances up and down, there is another set ofmuscles that is fed from another set of nerves that says,"One, two, three, O'Leary, one, two, ..." And while shedoes that, perhaps she smiles at the professor of physiologywho is watching her. That is involved, too!

    And then electricity. The forces of attraction, of plusand minus, are so strong that in any normal substance all theplusses and minuses are carefully balanced out, everythingpulled together with everything else. For a long time no oneeven noticed the phenomenon of electricity, except once in awhile when they rubbed a piece of amber and it attracted apiece of paper. And yet today we find, by playing with thesethings, that we have a tremendous amount of machineryinside. Yet science is still not thoroughly appreciated.

    To give an example, I read Faraday's Chemical Historyof a Candle, a set of six Christmas lectures for children. Thepoint of Faraday's lectures was that no matter what you lookat, if you look at it closely enough, youare involved in the entire universe. And so he got, bylooking at every feature of the candle, into combustion,chemistry, etc. But the introduction of the book, indescribing Faraday's life and some of his discoveries,explained that he had discovered that the amount ofelectricity necessary to do performic electrolysisof chemical substances is proportional to the number ofatoms which are separated divided by the valence. Itfurther explained that the principles he discovered areused today in chrome plating and the anodic coloringof aluminum, as well as in dozens of other industrialapplications. I do not like that statement. Here is whatFaraday said about his own discovery: "The atoms ofmatter are in some ways endowed or associated withelectrical powers, to which they owe their most strikingqualities, amongst them their mutual chemical affinity."He had discovered that the thing that determined howthe atoms went together, the thing that determined thecombinations of iron and oxygen which make ironoxide is that some of them are electrically plus and someof them are electrically minus, and they attract eachother in definite proportions. He also discovered thatelectricity comes in units, in atoms. Both were importantdiscoveries, but most exciting was that this was oneof the most dramatic moments in the history of science,one of those rare moments when two great fields cometogether and are unified. He suddenly found that twoapparently different things were different aspects of thesame thing. Electricity was being studied, and chemistry wasbeing studied. Suddenly they were two aspects of the samething--chemical changes with the results of electrical forces.And they are still understood that way. So to say merely thatthe principles are used in chrome plating is inexcusable.

    And the newspapers, as you know, have a standardfine for every discovery made in physiology today: "Thediscoverer said that the discovery may have uses in the cureof cancer." But they cannot explain the value of the thingitself.

    Trying to understand the way nature works involves amost terrible test of human reasoning ability. It involvessubtle trickery, beautiful tightropes of logic on which one hasto walk in order not to make a mistake in predicting what willhappen. The quantum mechanical and the relativity ideas areexamples of this.

    The third aspect of my subject is that of science as amethod of finding things out. This method is based on theprinciple that observation is the judge of whether somethingis so or not. All other aspects and characteristics of sciencecan be understood directly when we understand thatobservation is the ultimate and final judge of the truth of anidea. But "prove" used in this way really means "test," in thesame way that a hundred-proof alcohol is a test of thealcohol, and for people today the idea really should betranslated as, "The exception tests the rule." Or, put anotherway, "The exception proves that therule is wrong." That is the principle of science. Ifthere is an exception to any rule, and if it can be proved byobservation, that rule is wrong.

    The exceptions to any rule are most interesting inthemselves, for they show us that the old rule is wrong. Andit is most exciting, then, to find out what the right rule, if any,is. The exception is studied, along with other conditions thatproduce similar effects. The scientist tries to find moreexceptions and to determine the characteristics of theexceptions, a process that is continually exciting as itdevelops. He does not try to avoid showing that the rules arewrong; there is progress and excitement in the exactopposite. He tries to prove himself wrong as quickly aspossible.

    The principle that observation is the judge imposes asevere limitation to the kind of questions that can beanswered. They are limited to questions that you can put thisway: "if I do this, what will happen?" There are ways to tryit and see. Questions like, "should I do this?" and "what is thevalue of this?" are not of the same kind.

    But if a thing is not scientific, if it cannot be subjectedto the test of observation, this does not mean that it is dead,or wrong, or stupid. We are not trying to argue that scienceis somehow good and other things are somehow not good.Scientists take all those things that can be analyzed byobservation, and thus the things called science are found out.But there are some things left out, for which the methoddoes not work. This does not meanthat those things are unimportant. They are, in fact, in manyways the most important. In any decision for action, whenyou have to make up your mind what to do, there is always a"should" involved, and this cannot be worked out from"if I do this, what will happen?" alone. You say, "Sure, yousee what will happen, and then you decide whether you wantit to happen or not." But that is the step the scientist cannottake. You can figure out what is going to happen, but thenyou have to decide whether you like it that way or not.

    There are in science a number of technicalconsequences that follow from the principle of observationas judge. For example, the observation cannot be rough. Youhave to be very careful. There may have been a piece of dirtin the apparatus that made the color change; it was not whatyou thought. You have to check the observations verycarefully, and then recheck them, to be sure that youunderstand what all the conditions are and that you did notmisinterpret what you did.

    It is interesting that this thoroughness, which is a virtue,is often misunderstood. When someone says a thing hasbeen done scientifically, often all he means is that it has beendone thoroughly. I have heard people talk of the "scientific"extermination of the Jews in Germany. There was nothingscientific about it. It was only thorough. There was noquestion of making observations and then checking them inorder to determine something. In that sense, there were"scientific" exterminations of peoplein Roman times and in other periods when science wasnot so far developed as it is today and not much attentionwas paid to observation. In such cases, people should say"thorough" or "thoroughgoing," instead of "scientific."

    There are a number of special techniques associatedwith the game of making observations, and much of what iscalled the philosophy of science is concerned with adiscussion of these techniques. The interpretation of a resultis an example. To take a trivial instance, there is a famousjoke about a man who complains to a friend of a mysteriousphenomenon. The white horses on his farm eat more thanthe black horses. He worries about this and cannotunderstand it, until his friend suggests that maybe he hasmore white horses than black ones.

    It sounds ridiculous, but think how many times similarmistakes are made in judgments of various kinds. You say,"My sister had a cold, and in two weeks ..." It is one ofthose cases, if you think about it, in which there were morewhite horses. Scientific reasoning requires a certaindiscipline, and we should try to teach this discipline, becauseeven on the lowest level such errors are unnecessary today.

    Another important characteristic of science is itsobjectivity. It is necessary to look at the results ofobservation objectively, because you, the experimenter,might like one result better than another. You perform theexperiment several times, and because of irregularities, likepieces of dirt falling in, the result varies from time to time.You do not have everything under control. You likethe result to be a certain way, so the times it comes outthat way, you say, "See, it comes out this particular way."The next time you do the experiment it comes out different.Maybe there was a piece of dirt in it the first time, but youignore it.

    These things seem obvious, but people do not payenough attention to them in deciding scientific questions orquestions on the periphery of science. There could be acertain amount of sense, for example, in the way youanalyze the question of whether stocks went up or downbecause of what the President said or did not say.

    Another very important technical point is that the morespecific a rule is, the more interesting it is. The more definitethe statement, the more interesting it is to test. If someonewere to propose that the planets go around the sun becauseall planet matter has a kind of tendency for movement, a kindof motility, let us call it an "oomph," this theory could explaina number of other phenomena as well. So this is a goodtheory, is it not? No. It is nowhere near as good as aproposition that the planets move around the sun under theinfluence of a central force which varies exactly inversely asthe square of the distance from the center. The secondtheory is better because it is so specific; it is so obviouslyunlikely to be the result of chance. It is so definite that the barest errorin the movement can show that it is wrong; but the planetscould wobble all over the place, and, according to the firsttheory, you could say, "Well, that is the funny behavior ofthe `oomph.'"

    So the more specific the rule, the more powerful it is,the more liable it is to exceptions, and the more interestingand valuable it is to check.

    Words can be meaningless. If they are used in such away that no sharp conclusions can be drawn, as in myexample of "oomph," then the proposition they state isalmost meaningless, because you can explain almostanything by the assertion that things have a tendency tomotility. A great deal has been made of this byphilosophers, who say that words must be definedextremely precisely. Actually, I disagree somewhat withthis; I think that extreme precision of definition is often notworthwhile, and sometimes it is not possible--in fact mostlyit is not possible, but I will not get into that argument here.

    Most of what many philosophers say about science isreally on the technical aspects involved in trying to makesure the method works pretty well. Whether these technicalpoints would be useful in a field in which observation is notthe judge I have no idea. I am not going to say thateverything has to be done the same way when a method oftesting different from observation is used. In a different fieldperhaps it is not so important to be careful of the meaning ofwords or that the rules be specific, and so on. I do notknow.

    In all of this I have left out something very important. Isaid that observation is the judge of the truth of an idea.But where does the idea come from? The rapid progressand development of science requires that human beingsinvent something to test.

    It was thought in the Middle Ages that people simplymake many observations, and the observations themselvessuggest the laws. But it does not work that way. It takesmuch more imagination than that. So the next thing we haveto talk about is where the new ideas come from. Actually, itdoes not make any difference, as long as they come. Wehave a way of checking whether an idea is correct or notthat has nothing to do with where it came from. We simplytest it against observation. So in science we are notinterested in where an idea comes from.

    There is no authority who decides what is a goodidea. We have lost the need to go to an authority to find outwhether an idea is true or not. We can read an authorityand let him suggest something; we can try it out and find outif it is true or not. If it is not true, so much the worse--so the"authorities" lose some of their "authority."

    The relations among scientists were at first veryargumentative, as they are among most people. This wastrue in the early days of physics, for example. But in physicstoday the relations are extremely good. A scientificargument is likely to involve a great deal of laughterand uncertainty on both sides, with both sides thinking upexperiments and offering to bet on the outcome. In physicsthere are so many accumulated observations that it is almostimpossible to think of a new idea which is different from allthe ideas that have been thought of before and yet thatagrees with all the observations that have already beenmade. And so if you get anything new from anyone,anywhere, you welcome it, and you do not argue about whythe other person says it is so.

    Many sciences have not developed this far, and thesituation is the way it was in the early days of physics, whenthere was a lot of arguing because there were not so manyobservations. I bring this up because it is interesting thathuman relationships, if there is an independent way ofjudging truth, can become unargumentative.

    Most people find it surprising that in science there is nointerest in the background of the author of an idea or in hismotive in expounding it. You listen, and if it sounds like athing worth trying, a thing that could be tried, is different, andis not obviously contrary to something observed before, itgets exciting and worthwhile. You do not have to worryabout how long he has studied or why he wants you to listento him. In that sense it makes no difference where the ideascome from. Their real origin is unknown; we call it theimagination of the human brain, the creative imagination--it isknown; it is just one of those "oomphs."

    It is surprising that people do not believe thatthere is imagination in science. It is a very interesting kind ofimagination, unlike that of the artist. The great difficulty is intrying to imagine something that you have never seen, that isconsistent in every detail with what has already been seen,and that is different from what has been thought of;furthermore, it must be definite and not a vague proposition.That is indeed difficult.

    Incidentally, the fact that there are rules at all to bechecked is a kind of miracle; that it is possible to find a rule,like the inverse square law of gravitation, is some sort ofmiracle. It is not understood at all, but it leads to thepossibility of prediction--that means it tells you what youwould expect to happen in an experiment you have not yetdone.

    It is interesting, and absolutely essential, that the variousrules of science be mutually consistent. Since theobservations are all the same observations, one rule cannotgive one prediction and another rule another prediction. Thus,science is not a specialist business; it is completely universal.I talked about the atoms in physiology; I talked about theatoms in astronomy, electricity, chemistry. They areuniversal; they must be mutually consistent. You cannot juststart off with a new thing that cannot be made of atoms.

    It is interesting that reason works in guessing at therules, and the rules, at least in physics, become reduced. Igave an example of the beautiful reduction of the rulesin chemistry and electricity into one rule, but there are manymore examples.

    The rules that describe nature seem to bemathematical. This is not a result of the fact that observationis the judge, and it is not a characteristic necessity of sciencethat it be mathematical. It just turns out that you can statemathematical laws, in physics at least, which work to makepowerful predictions. Why nature is mathematical is, again, amystery.

    I come now to an important point. The old laws may bewrong. How can an observation be incorrect? If it has beencarefully checked, how can it be wrong? Why are physicistsalways having to change the laws? The answer is, first, thatthe laws are not the observations and, second, thatexperiments are always inaccurate. The laws are guessedlaws, extrapolations, not something that the observationsinsist upon. They are just good guesses that have gonethrough the sieve so far. And it turns out later that the sievenow has smaller holes than the sieves that were used before,and this time the law is caught. So the laws are guessed;they are extrapolations into the unknown. You do not knowwhat is going to happen, so you take a guess.

    For example, it was believed--it was discovered--thatmotion does not affect the weight of a thing--that if you spina top and weigh it, and then weigh it when it has stopped, itweighs the same. That is the result of an observation. Butyou cannot weigh something to theinfinitesimal number of decimal places, parts in a billion. Butwe now understand that a spinning top weighs more than atop which is not spinning by a few parts in less than a billion.If the top spins fast enough so that the speed of the edgesapproaches 186,000 miles a second, the weight increase isappreciable--but not until then. The first experiments wereperformed with tops that spun at speeds much lower than186,000 miles a second. It seemed then that the mass of thetop spinning and not spinning was exactly the same, andsomeone made a guess that the mass never changes.

    How foolish! What a fool! It is only a guessed law, anextrapolation. Why did he do something so unscientific?There was nothing unscientific about it; it was only uncertain.It would have been unscientific not to guess. It has to bedone because the extrapolations are the only things that haveany real value. It is only the principle of what you think willhappen in a case you have not tried that is worth knowingabout. Knowledge is of no real value if all you can tell me iswhat happened yesterday. It is necessary to tell what willhappen tomorrow if you do something--not necessary, but fun.Only you must be willing to stick your neck out.

    Every scientific law, every scientific principle, everystatement of the results of an observation is some kind of asummary which leaves out details, because nothing can bestated precisely. The man simply forgot--he should havestated the law "The mass doesn't change muchwhen the speed isn't too high." The game is to make aspecific rule and then see if it will go through the sieve. Sothe specific guess was that the mass never changes at all.Exciting possibility! It does no harm that it turned out not tobe the case. It was only uncertain, and there is no harm inbeing uncertain. It is better to say something and not be surethan not to say anything at all.

    It is necessary and true that all of the things we say inscience, all of the conclusions, are uncertain, because theyare only conclusions. They are guesses as to what is goingto happen, and you cannot know what will happen, becauseyou have not made the most complete experiments.

    It is curious that the effect on the mass of a spinningtop is so small you may say, "Oh, it doesn't make anydifference." But to get a law that is right, or at least one thatkeeps going through the successive sieves, that goes on formany more observations, requires a tremendous intelligenceand imagination and a complete revamping of our philosophy,our understanding of space and time. I am referring to therelativity theory. It turns out that the tiny effects that turn upalways require the most revolutionary modifications of ideas.

    Scientists, therefore, are used to dealing with doubt anduncertainty. All scientific knowledge is uncertain. Thisexperience with doubt and uncertainty is important. I believethat it is of very great value, and one that extends beyond thesciences. I believe that to solve anyproblem that has never been solved before, you have toleave the door to the unknown ajar. You have to permit thepossibility that you do not have it exactly right. Otherwise, ifyou have made up your mind already, you might not solve it.

    When the scientist tells you he does not know theanswer, he is an ignorant man. When he tells you he has ahunch about how it is going to work, he is uncertain aboutit. When he is pretty sure of how it is going to work, and hetells you, "This is the way it's going to work, I'll bet," he stillis in some doubt. And it is of paramount importance, in orderto make progress, that we recognize this ignorance and thisdoubt. Because we have the doubt, we then propose lookingin new directions for new ideas. The rate of the developmentof science is not the rate at which you make observationsalone but, much more important, the rate at which you createnew things to test.

    If we were not able or did not desire to look in any newdirection, if we did not have a doubt or recognize ignorance,we would not get any new ideas. There would be nothingworth checking, because we would know what is true. Sowhat we call scientific knowledge today is a body ofstatements of varying degrees of certainty. Some of themare most unsure; some of them are nearly sure; but none isabsolutely certain. Scientists are used to this. We know thatit is consistent to be able to live and not know. Some peoplesay, "How can you live without knowing?" I do not knowwhat they mean. I always livewithout knowing. That is easy. How you get to know iswhat I want to know.

    This freedom to doubt is an important matter in thesciences and, I believe, in other fields. It was born of astruggle. It was a struggle to be permitted to doubt, to beunsure. And I do not want us to forget the importance of thestruggle and, by default, to let the thing fall away. I feel aresponsibility as a scientist who knows the great value of asatisfactory philosophy of ignorance, and the progress madepossible by such a philosophy, progress which is the fruit offreedom of thought. I feel a responsibility to proclaim thevalue of this freedom and to teach that doubt is not to befeared, but that it is, to be welcomed as the possibility of anew potential for human beings. If you know that you arenot sure, you have a chance to improve the situation. I wantto demand this freedom for future generations.

    Doubt is clearly a value in the sciences. Whether it is inother fields is an open question and an uncertain matter. Iexpect in the next lectures to discuss that very point and totry to demonstrate that it is important to doubt and that doubtis not a fearful thing, but a thing of very great value.

Continues...

Excerpted from The Meaning of It Allby Richard Phillips Feynman Copyright © 2005 by Richard Phillips Feynman. Excerpted by permission.
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Edition details

• Publisher: Basic Books
• Publication date: 2005
• ISBN 10: 0465023940
• ISBN 13: 9780465023943
• Binding: Paperback
• Language: English
• Number of pages: 144