I
want to address myself directly to the impact of science on man’s ideas in
other fields, a subject Mr. John Danz particularly wanted to be discussed. In
the first of these lectures I will talk about the nature of science and
emphasize particularly the existence of doubt and uncertainty. In the second
lecture I will discuss the impact of scientific views on political questions,
in particular the question of national enemies, and on religious questions. And
in the third lecture I will describe how society looks to me—I could say how
society looks to a scientific man, but it is only how it looks to me—and what
future scientific discoveries may produce in terms of social problems.
What
do I know of religion and politics? Several friends in the physics departments
here and in other places laughed and said, “I’d like to come and hear what you
have to say. I never knew you were interested very much in those things.” They
mean, of course, I am interested, but I would not dare to talk about them.
In
talking about the impact of ideas in one field on ideas in another field, one
is always apt to make a fool of oneself. In these days of specialization there
are too few people who have such a deep understanding of two departments of our
knowledge that they do not make fools of themselves in one or the other.
The
ideas I wish to describe are old ideas. There is practically nothing that I am
going to say tonight that could not easily have been said by philosophers of
the seventeenth century. Why repeat all this? Because there are new generations
born every day. Because there are great ideas developed in the history of man,
and these ideas do not last unless they are passed purposely and clearly from
generation to generation.
Many
old ideas have become such common knowledge that it is not necessary to talk
about or explain them again. But the ideas associated with the problems of the
development of science, as far as I can see by looking around me, are not of
the kind that everyone appreciates. It is 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.
Now
in this difficult business of talking about the impact of the ideas of one
field on those of another, I shall start at the end that I know. I do know
about science. I know its ideas and its methods, its attitudes toward
knowledge, the sources of its progress, its mental discipline. And therefore,
in this first lecture, I shall talk about the science that I know, and I shall
leave the more ridiculous of my 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 one of three things, or a mixture
of them. I do not think we need to be precise—it is not always a good idea to
be too precise. Science means, sometimes, a special method of finding things
out. Sometimes it means the body of knowledge arising from the things found
out. It may also mean the new things you can do when you have found something
out, or the actual doing of new things. This last field is usually called
technology—but if you look at the science section in Time magazine you will
find it covers about 50 percent what new things are found out and about 50
percent what new things can be and are being done. And so the popular
definition of science is partly technology, too.
I
want to discuss these three aspects of science in reverse order. I will begin
with the new things that you can do—that is, with technology. The most obvious
characteristic of science is its application, the fact that as a consequence of
science one has a power to do things. And the effect this power has had need
hardly be mentioned. The whole industrial revolution would almost have been
impossible without the development of science. The possibilities today of
producing quantities of food adequate for such a large population, of
controlling sickness—the very fact that there can be free men without the
necessity of slavery for full production—are very likely the result of the
development of scientific means of production.
Now
this power to do things carries with it no instructions on how to use it,
whether to use it for good or for evil. The product of this power is either
good or evil, depending on how it is used. We like improved production, but we
have problems with automation. We are happy with the development of medicine,
and then we worry about the number of births and the fact that no one dies from
the diseases we have eliminated. Or else, with the same knowledge of bacteria,
we have hidden laboratories in which men are working as hard as they can to
develop bacteria for which no one else will be able to find a cure. We are
happy with the development of air transportation and are impressed by the great
airplanes, but we are aware also of the severe horrors of air war. We are
pleased by the ability to communicate between nations, and then we worry about
the fact that we can be snooped upon so easily. We are excited by the fact that
space can now be entered; well, we will undoubtedly have a difficulty there,
too. The most famous of all these imbalances is the development of nuclear
energy and its obvious problems.
Is
science of any value?
I
think a power to do something is of value.Whether the result is a good thing or
a bad thing depends on how it is used, 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 something that you will never forget.” And then he said, “To
every man is given the key to the gates of heaven. The same key opens the gates
of hell.”
And
so it is with science. In a way it is a key to the gates of heaven, and the
same key opens the gates of hell, and we do not have any instructions as to
which is which gate. Shall we throw away the key and never have a way to enter
the gates of heaven? Or shall we struggle with the problem of which is the best
way to use the key? That is, of course, a very serious question, but I think
that we cannot deny the value of the key to the gates of heaven.
All
the major problems of the relations between society and science lie in this
same area. When the scientist is told that he must be more responsible for his
effects on society, it is the applications of science that are referred to. If
you work to develop nuclear energy you must realize also that it can be used
harmfully. Therefore, you would expect that, in a discussion of this kind by a
scientist, this would be the most important topic. But I will not talk about it
further. I think that to say these are scientific problems is an exaggeration.
They are far more humanitarian problems. The fact that how to work the power is
clear, but how to control it is not, is something not so scientific and is not
something that the scientist 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 to teach physics. There was a Point Four program
in those days, which was very exciting—everyone was going to help the
underdeveloped countries. What they needed, of course, was technical know-how.
In
Brazil I lived in the city of Rio. In Rio there are hills on which are homes
made with broken pieces of wood from old signs and so forth. The people are
extremely poor. They have no sewers and no water. In order to get water they
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.
The people fill their cans with water and carry them up the hills. And later
you see the water dripping down the hill in dirty sewage. It is a pitiful
thing.
Right
next to these hills are the exciting buildings of the Copacabana beach,
beautiful apartments, and so on.
And
I said to my friends in the Point Four program, “Is this a problem of technical
know-how? They don’t know how to put a pipe up the hill? They don’t know how to
put a pipe to the top of the hill so that the people can at least walk uphill
with the empty cans and downhill with the full cans?”
So
it is not a problem of technical know-how. Certainly not, because in the
neighboring apartment buildings there are pipes, and there are pumps. We
realize that now. Now we think it is a problem of economic assistance, and we
do not know whether that really works or not. And the question of how much it
costs to put a pipe and a pump to the top of each of the hills is not one that
seems worth discussing, to me.
Although
we do not know how to solve the problem, I would like to point out that we
tried two things, technical know-how and economic assistance. We are discouraged
with them both, and we are trying something else. As you will see later, I find
this encouraging. I think that to keep trying new solutions is the way to do
everything.
Those,
then are the practical aspects of science, the new things that you can do. They
are so obvious that we do not need to speak about them further.
The
next aspect of science is its contents, the things that have been found out.
This is the yield. This is the gold. This is the excitement, the pay you get
for all the disciplined thinking and hard work. The work is not done for the
sake of an application. It is done for the excitement of what is found out.
Perhaps most of you know this. But to those of you who do not know it, it is
almost impossible for me to convey in a lecture this important aspect, this
exciting part, the real reason for science. And without understanding this you
miss the whole point. You cannot understand science and its relation to
anything else unless you understand and appreciate the great adventure of our
time. You do not live in your time unless you understand that this is a
tremendous adventure and a wild and exciting thing.
Do
you think it is dull? It isn’t. It is most difficult to convey, but perhaps I
can give some idea of it. Let me start anywhere, with any idea.
For
instance, the ancients believed that the earth was the back of an elephant that
stood on a tortoise that swam in a bottomless sea. Of course, what held up the
sea 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 it today. Is that a dull idea? The world
is a spinning ball, and people 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 whirl around the
sun. That is more romantic, more exciting. And what holds us? The force of
gravitation, which is not only a thing of the earth but is the thing that makes
the earth round in the first place, holds the sun together and keeps us running
around the sun in our perpetual attempt to stay away. This gravity holds its
sway not only on the stars but between the stars; it holds them in the great
galaxies for miles and miles in all directions.
This
universe has been described by many, but it just goes on, with its edge as
unknown as the bottom of the bottomless sea of the other idea—just as
mysterious, just as awe-inspiring, and just as incomplete as the poetic
pictures that came before.
But
see that the imagination of nature is far, far greater than the imagination of
man. No one who did not have some inkling of this through observations could
ever have imagined such a marvel as nature is.
Or
the earth and time. Have you read anywhere, by any 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 without anything alive on it. For
billions of years this ball was spinning with its sunsets and its waves and the
sea and the noises, and there was no thing alive to appreciate it. Can you
conceive, can you appreciate or fit into your ideas what can be the meaning of
a world without a living thing on it? We are so used to looking at the world
from the point of view of living things that we cannot understand what it means
not to be alive, and yet most of the time the world had nothing alive on it.
And in most places in the universe today there probably is nothing alive.
Or
life itself. The internal machinery of life, the chemistry of the parts, is
something beautiful. And it turns out that all life is interconnected with all
other life. There is a part of chlorophyll, an important chemical in the oxygen
processes in plants, that has a kind of square pattern; it is a rather pretty
ring called a benzine ring. And far removed from the plants are animals like
ourselves, and in our oxygen-containing systems, in the blood, the hemoglobin,
there are the same interesting and peculiar square rings. There is iron in the
center of them instead of magnesium, so they are not green but red, but they
are the same rings.
The
proteins of bacteria and the proteins of humans are the same. In fact it has
recently been found that the protein-making machinery in the bacteria can be
given orders from material from the red cells to produce red cell proteins. So
close is life to life. The universality of the deep chemistry of living things
is indeed a fantastic and beautiful thing. And all the time we human beings
have been too proud even to recognize our kinship with the animals.
Or
there are the atoms. Beautiful—mile upon mile of one ball after another ball in
some repeating pattern in a crystal. Things that look quiet and still, like a
glass of water with a covered top that has been sitting for several days, are
active all the time; the atoms are leaving the surface, bouncing around inside,
and coming back. What looks still to our crude eyes is a wild and dynamic
dance.
And,
again, it has been discovered that all the world is made of the same atoms,
that the stars are of the same stuff as ourselves. It then becomes a question
of where our stuff came from. Not just where did life come from, or where did
the earth come from, but where did the stuff of life and of the earth come
from? It looks as if it was belched from some exploding star, much as some of
the stars are exploding now. So this piece of dirt waits four and a half
billion years and evolves and changes, and now a strange creature stands here
with instruments and talks to the strange creatures in the audience. What a
wonderful world!
Or
take the physiology of human beings. It makes no difference what I talk about.
If you look closely enough at anything, you will see that there is nothing more
exciting than the truth, the pay dirt of the scientist, discovered by his
painstaking efforts.
In
physiology you can think of pumping blood, the exciting movements of a girl
jumping a jump rope. What goes on inside? The blood pumping, the
interconnecting nerves—how quickly the influences of the muscle nerves feed
right back to the brain to say, “Now we have touched the ground, now increase
the tension so I do not hurt the heels.” And as the girl dances up and down,
there is another set of muscles that is fed from another set of nerves that
says, “One, two, three, O’Leary, one, two, …” And while she does that, perhaps
she smiles at the professor of physiology who is watching her. That is
involved, too!
And
then electricity The forces of attraction, of plus and minus, are so strong
that in any normal substance all the plusses and minuses are carefully balanced
out, everything pulled together with everything else. For a long time no one
even noticed the phenomenon of electricity, except once in a while when they
rubbed a piece of amber and it attracted a piece of paper. And yet today we
find, by playing with these things, that we have a tremendous amount of
machinery inside. Yet science is still not thoroughly appreciated.
To
give an example, I read Faraday’s Chemical History of a Candle, a set of six
Christmas lectures for children. The point of Faraday’s lectures was that no
matter what you look at, if you look at it closely enough, you are involved in
the entire universe. And so he got, by looking at every feature of the candle,
into combustion, chemistry, etc. But the introduction of the book, in
describing Faraday’s life and some of his discoveries, explained that he had
discovered that the amount of electricity necessary to perform electrolysis of
chemical substances is proportional to the number of atoms which are separated
divided by the valence. It further explained that the principles he discovered
are used today in chrome plating and the anodic coloring of aluminum, as well
as in dozens of other industrial applications. I do not like that statement.
Here is what Faraday said about his own discovery: “The atoms of matter are in
some ways endowed or associated with electrical powers, to which they owe their
most striking qualities, amongst them their mutual chemical affinity.” He had
discovered that the thing that determined how the atoms went together, the
thing that determined the combinations of iron and oxygen which make iron oxide
is that some of them are electrically plus and some of them are electrically
minus, and they attract each other in definite proportions. He also discovered
that electricity comes in units, in atoms. Both were important discoveries, but
most exciting was that this was one of the most dramatic moments in the history
of science, one of those rare moments when two great fields come together and
are unified. He suddenly found that two apparently different things were
different aspects of the same thing. Electricity was being studied, and
chemistry was being studied. Suddenly they were two aspects of the same
thing—chemical changes with the results of electrical forces. And they are
still understood that way. So to say merely that the principles are used in
chrome plating is inexcusable.
And
the newspapers, as you know, have a standard line for every discovery made in
physiology today: “The discoverer said that the discovery may have uses in the
cure of cancer.” But they cannot explain the value of the thing itself.
Trying
to understand the way nature works involves a most terrible test of human
reasoning ability. It involves subtle trickery, beautiful tightropes of logic
on which one has to walk in order not to make a mistake in predicting what will
happen. The quantum mechanical and the relativity ideas are examples of this.
The
third aspect of my subject is that of science as a method of finding things out.
This method is based on the principle that observation is the judge of whether
something is so or not. All other aspects and characteristics of science can be
understood directly when we understand that observation is the ultimate and
final judge of the truth of an idea. But “prove” used in this way really means
“test,” in the same way that a hundred-proof alcohol is a test of the alcohol,
and for people today the idea really should be translated as, “The exception
tests the rule.” Or, put another way, “The exception proves that the rule is
wrong.” That is the principle of science. If there is an exception to any rule,
and if it can be proved by observation, that rule is wrong.
The
exceptions to any rule are most interesting in themselves, for they show us
that the old rule is wrong. And it is most exciting, then, to find out what the
right rule, if any, is. The exception is studied, along with other conditions
that produce similar effects. The scientist tries to find more exceptions and
to determine the characteristics of the exceptions, a process that is
continually exciting as it develops. He does not try to avoid showing that the
rules are wrong; there is progress and excitement in the exact opposite. He
tries to prove himself wrong as quickly as possible.
The
principle that observation is the judge imposes a severe limitation to the kind
of questions that can be answered. They are limited to questions that you can
put this way: “if I do this, what will happen?” There are ways to try it and
see. Questions like, “should I do this?” and “what is the value of this?” are
not of the same kind.
But
if a thing is not scientific, if it cannot be subjected to the test of
observation, this does not mean that it is dead, or wrong, or stupid. We are
not trying to argue that science is somehow good and other things are somehow
not good. Scientists take all those things that can be analyzed by observation,
and thus the things called science are found out. But there are some things
left out, for which the method does not work. This does not mean that those
things are unimportant. They are, in fact, in many ways the most important. In
any decision for action, when you 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, you see what will happen, and
then you decide whether you want it to happen or not.” But that is the step the
scientist cannot take. You can figure out what is going to happen, but then you
have to decide whether you like it that way or not.
There
are in science a number of technical consequences that follow from the
principle of observation as judge. For example, the observation cannot be
rough. You have to be very careful. There may have been a piece of dirt in the
apparatus that made the color change; it was not what you thought. You have to
check the observations very carefully, and then recheck them, to be sure that
you understand what all the conditions are and that you did not misinterpret what
you did.
It
is interesting that this thoroughness, which is a virtue, is often
misunderstood. When someone says a thing has been done scientifically, often
all he means is that it has been done thoroughly. I have heard people talk of
the “scientific” extermination of the Jews in Germany. There was nothing
scientific about it. It was only thorough. There was no question of making
observations and then checking them in order to determine something. In that
sense, there were “scientific” exterminations of people in Roman times and in
other periods when science was not so far developed as it is today and not much
attention was paid to observation. In such cases, people should say “thorough”
or “thoroughgoing,” instead of “scientific.”
There
are a number of special techniques associated with the game of making
observations, and much of what is called the philosophy of science is concerned
with a discussion of these techniques. The interpretation of a result is an
example. To take a trivial instance, there is a famous joke about a man who
complains to a friend of a mysterious phenomenon. The white horses on his farm
eat more than the black horses. He worries about this and cannot understand it,
until his friend suggests that maybe he has more white horses than black ones.
It
sounds ridiculous, but think how many times similar mistakes are made in
judgments of various kinds. You say, “My sister had a cold, and in two weeks …”
It is one of those cases, if you think about it, in which there were more white
horses. Scientific reasoning requires a certain discipline, and we should try
to teach this discipline, because even on the lowest level such errors are
unnecessary today.
Another
important characteristic of science is its objectivity. It is necessary to look
at the results of observation objectively, because you, the experimenter, might
like one result better than another. You perform the experiment several times,
and because of irregularities, like pieces of dirt falling in, the result
varies from time to time. You do not have everything under control. You like
the result to be a certain way, so the times it comes out that 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
you ignore it.
These
things seem obvious, but people do not pay enough attention to them in deciding
scientific questions or questions on the periphery of science. There could be a
certain amount of sense, for example, in the way you analyze the question of
whether stocks went up or down because of what the President said or did not
say.
Another
very important technical point is that the more specific a rule is, the more
interesting it is. The more definite the statement, the more interesting it is
to test. If someone were to propose that the planets go around the sun because
all planet matter has a kind of tendency for movement, a kind of motility, let
us call it an “oomph,” this theory could explain a number of other phenomena as
well. So this is a good theory, is it not? No. It is nowhere near as good as a
proposition that the planets move around the sun under the influence of a
central force which varies exactly inversely as the square of the distance from
the center. The second theory is better because it is so specific; it is so
obviously unlikely to be the result of chance. It is so definite that the
barest error in the movement can show that it is wrong; but the planets could
wobble all over the place, and, according to the first theory, you could say,
“Well, that is the funny behavior of the ‘oomph.’”
So
the more specific the rule, the more powerful it is, the more liable it is to
exceptions, and the more interesting and valuable it is to check.
Words
can be meaningless. If they are used in such a way that no sharp conclusions
can be drawn, as in my example of “oomph,” then the proposition they state is
almost meaningless, because you can explain almost anything by the assertion
that things have a tendency to motility. A great deal has been made of this by
philosophers, who say that words must be defined extremely precisely. Actually,
I disagree somewhat with this; I think that extreme precision of definition is
often not worthwhile, and sometimes it is not possible—in fact mostly it is not
possible, but I will not get into that argument here.
Most
of what many philosophers say about science is really on the technical aspects
involved in trying to make sure the method works pretty well. Whether these
technical points would be useful in a field in which observation is not the
judge I have no idea. I am not going to say that everything has to be done the
same way when a method of testing different from observation is used. In a
different field perhaps it is not so important to be careful of the meaning of
words or that the rules be specific, and so on. I do not know.
In
all of this I have left out something very important. I said that observation
is the judge of the truth of an idea. But where does the idea come from? The
rapid progress and development of science requires that human beings invent
something to test.
It
was thought in the Middle Ages that people simply make many observations, and
the observations themselves suggest the laws. But it does not work that way. It
takes much more imagination than that. So the next thing we have to talk about
is where the new ideas come from. Actually, it does not make any difference, as
long as they come. We have a way of checking whether an idea is correct or not
that has nothing to do with where it came from. We simply test it against
observation. So in science we are not interested in where an idea comes from.
There
is no authority who decides what is a good idea. We have lost the need to go to
an authority to find out whether an idea is true or not. We can read an
authority and let him suggest something; we can try it out and find out if 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 very argumentative, as they are among
most people. This was true in the early days of physics, for example. But in
physics today the relations are extremely good. A scientific argument is likely
to involve a great deal of laughter and uncertainty on both sides, with both
sides thinking up experiments and offering to bet on the outcome. In physics
there are so many accumulated observations that it is almost impossible to
think of a new idea which is different from all the ideas that have been
thought of before and yet that agrees with all the observations that have
already been made. And so if you get anything new from anyone, anywhere, you
welcome it, and you do not argue about why the other person says it is so.
Many
sciences have not developed this far, and the situation is the way it was in
the early days of physics, when there was a lot of arguing because there were
not so many observations. I bring this up because it is interesting that human
relationships, if there is an independent way of judging truth, can become
unargumentative.
Most
people find it surprising that in science there is no interest in the
background of the author of an idea or in his motive in expounding it. You
listen, and if it sounds like a thing worth trying, a thing that could be tried,
is different, and is not obviously contrary to something observed before, it
gets exciting and worthwhile. You do not have to worry about how long he has
studied or why he wants you to listen to him. In that sense it makes no
difference where the ideas come from. Their real origin is unknown; we call it
the imagination of the human brain, the creative imagination—it is known; it is
just one of those “oomphs.”
It
is surprising that people do not believe that there is imagination in science.
It is a very interesting kind of imagination, unlike that of the artist. The
great difficulty is in trying to imagine something that you have never seen,
that is consistent 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 be checked is a kind of miracle; that
it is possible to find a rule, like the inverse square law of gravitation, is
some sort of miracle. It is not understood at all, but it leads to the
possibility of prediction—that means it tells you what you would expect to
happen in an experiment you have not yet done.
It
is interesting, and absolutely essential, that the various rules of science be
mutually consistent. Since the observations are all the same observations, one
rule cannot give 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 the atoms in astronomy,
electricity, chemistry. They are universal; they must be mutually consistent.
You cannot just start off with a new thing that cannot be made of atoms.
It
is interesting that reason works in guessing at the rules, and the rules, at
least in physics, become reduced. I gave an example of the beautiful reduction
of the rules in chemistry and electricity into one rule, but there are many
more examples.
The
rules that describe nature seem to be mathematical. This is not a result of the
fact that observation is the judge, and it is not a characteristic necessity of
science that it be mathematical. It just turns out that you can state
mathematical laws, in physics at least, which work to make powerful
predictions. Why nature is mathematical is, again, a mystery.
I
come now to an important point. The old laws may be wrong. How can an
observation be incorrect? If it has been carefully checked, how can it be
wrong? Why are physicists always having to change the laws? The answer is,
first, that the laws are not the observations and, second, that experiments are
always inaccurate. The laws are guessed laws, extrapolations, not something
that the observations insist upon. They are just good guesses that have gone
through the sieve so far. And it turns out later that the sieve now 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
know what is going to happen, so you take a guess.
For
example, it was believed—it was discovered— that motion does not affect the
weight of a thing—that if you spin a top and weigh it, and then weigh it when it
has stopped, it weighs the same. That is the result of an observation. But you
cannot weigh something to the infinitesimal number of decimal places, parts in
a billion. But we now understand that a spinning top weighs more than a top
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 edges approaches 186,000 miles a second,
the weight increase is appreciable—but not until then. The first experiments
were performed with tops that spun at speeds much lower than 186,000 miles a
second. It seemed then that the mass of the top spinning and not spinning was
exactly the same, and someone made a guess that the mass never changes.
How
foolish! What a fool! It is only a guessed law, an extrapolation. 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 be done
because the extrapolations are the only things that have any real value. It is
only the principle of what you think will happen in a case you have not tried
that is worth knowing about. Knowledge is of no real value if all you can tell
me is what happened yesterday. It is necessary to tell what will happen
tomorrow if you do something—not only necessary, but fun. Only you must be
willing to stick your neck out.
Every
scientific law, every scientific principle, every statement of the results of
an observation is some kind of a summary which leaves out details, because
nothing can be stated precisely. The man simply forgot—he should have stated
the law “The mass doesn’t change much when the speed isn’t too high.” The game
is to make a specific rule and then see if it will go through the sieve. So the
specific guess was that the mass never changes at all. Exciting possibility! It
does no harm that it turned out not to be the case. It was only uncertain, and
there is no harm in being uncertain. It is better to say something and not be
sure than not to say anything at all.
It
is necessary and true that all of the things we say in science, all of the
conclusions, are uncertain, because they are only conclusions. They are guesses
as to what is going to happen, and you cannot know what will happen, because
you have not made the most complete experiments.
It
is curious that the effect on the mass of a spinning top is so small you may
say, “Oh, it doesn’t make any difference.” But to get a law that is right, or
at least one that keeps going through the successive sieves, that goes on for
many more observations, requires a tremendous intelligence and imagination and
a complete revamping of our philosophy, our understanding of space and time. I
am referring to the relativity theory. It turns out that the tiny effects that
turn up always require the most revolutionary modifications of ideas.
Scientists,
therefore, are used to dealing with doubt and uncertainty. All scientific
knowledge is uncertain. This experience with doubt and uncertainty is
important. I believe that it is of very great value, and one that extends
beyond the sciences. I believe that to solve any problem that has never been
solved before, you have to leave the door to the unknown ajar. You have to
permit the possibility that you do not have it exactly right. Otherwise, if you
have made up your mind already, you might not solve it.
When
the scientist tells you he does not know the answer, he is an ignorant man.
When he tells you he has a hunch about how it is going to work, he is uncertain
about it. When he is pretty sure of how it is going to work, and he tells you,
“This is the way it’s going to work, I’ll bet,” he still is in some doubt. And
it is of paramount importance, in order to make progress, that we recognize
this ignorance and this doubt. Because we have the doubt, we then propose looking
in new directions for new ideas. The rate of the development of science is not
the rate at which you make observations alone but, much more important, the
rate at which you create new things to test.
If
we were not able or did not desire to look in any new direction, if we did not
have a doubt or recognize ignorance, we would not get any new ideas. There
would be nothing worth checking, because we would know what is true. So what we
call scientific knowledge today is a body of statements of varying degrees of
certainty. Some of them are most unsure; some of them are nearly sure; but none
is absolutely certain. Scientists are used to this. We know that it is
consistent to be able to live and not know. Some people say, “How can you live
without knowing?” I do not know what they mean. I always live without knowing.
That is easy. How you get to know is what I want to know.
This
freedom to doubt is an important matter in the sciences and, I believe, in
other fields. It was born of a struggle. It was a struggle to be permitted to
doubt, to be unsure. And I do not want us to forget the importance of the
struggle and, by default, to let the thing fall away. I feel a responsibility
as a scientist who knows the great value of a satisfactory philosophy of
ignorance, and the progress made possible by such a philosophy, progress which
is the fruit of freedom of thought. I feel a responsibility to proclaim the
value of this freedom and to teach that doubt is not to be feared, but that it
is to be welcomed as the possibility of a new potential for human beings. If
you know that you are not sure, you have a chance to improve the situation. I
want to demand this freedom for future generations.
Doubt
is clearly a value in the sciences. Whether it is in other fields is an open question
and an uncertain matter. I expect in the next lectures to discuss that very
point and to try to demonstrate that it is important to doubt and that doubt is
not a fearful thing, but a thing of very great value.