cAbout fifteen years ago when I first started
in this whole field of philosophy of
science, I thought like many of you here
that although scientific theories change,
there is something unchangeable in science.
That something is the scientific method.
My initial idea was that the only
thing that remains to be done is to sit
down and try to explicate those criteria.
Just to write them down! As I read
and read more and more things, I have come to
discover what philosophers actually had
discovered twenty five years before that.
The idea that there is no such thing as
a universal scientific method, a fixed
scientific method. There is no such thing.
So what do you do in that situation?
The question immediately becomes why it is that we prefer the hypothetico-
deductive method here and not the
Aristotelian-Medieval method there?
After all, if everyone is free to
choose her own method, chances are you
are going to have your theory as the best
available theory and I'm going to have my theory
as the best available theory. Your theory
will be better by your own standards.
My theory will be better by my own
standards. Everyone will be happy.
So what do you do?
The question is: is the choice of methods
arbitrary? Or is there a logic that
governs the process of scientific change? 
Is scientific change rational?
A law-governed process? We know that theories change, methods change. Is there any
internal mechanism? Is there any logic
that governs this change? Another way of
saying this: can there be a 
general descriptive theory of science?
Can we actually have a theory that
explains how theories and methods change?
We take this question. You can say "yes" or you can say "no". If you say "yes", your position
is called generalism.  Generalists
believe that there can be a general
descriptive theory of scientific change, a
theory that explains all the transitions
from one theory to the next and from one
method to the next. This is an important
part: not just theories but also methods.
The accepted view nowadays is that of
particularists. These guys believe that
science is so disunited, that science is
so diverse in different times and in
different fields of inquiry that there
cannot possibly be such a thing as a
general theory of scientific change.
If you ask those guys, "Why is it that you
believe that there can be no such thing
as a general theory of scientific change?"
They normally have two reasons.
The first reason is that they say there
is no universal and unchangeable method
of science. We all know that there's
no such thing. They say since the method
of science are changeable therefore there
can be no general theory of science.
There is a strong argument: not only
there is no fixed method of science but
there are no universal features; nothing
is permanent in science; there is nothing
universal and nothing permanent in
science. So the second argument is
stronger than the first one. The first
one only says the method is changeable.
The second one says everything is
changeable. There is no fixed features in science.
So the question that I have here: why
would anyone think nowadays that there
after all there can be such a thing as a
general theory of scientific change?
This is the question. I'm going to give you a few examples of how methods change. And my point
is going to be that there is after all a
certain mechanism which all transitions
from one method to the next share. There
is the same mechanism in place. Let's
take a very basic example. Suppose
somebody came up with a drug,
an anti-depressant, let's call it X
anti-depressant. How do you test it? Well,
the initial attitude would be - if you
don't know anything about drug testing -
you say, "Well, if the claim is that the
drug is therapeutically efficient, you
just have to find people who suffer from
the condition - like that group of people -
not necessarily famous philosophers but
can be anyone as long as they suffer
from the condition -
and give them the drug. If there is a
notable improvement, you say that the
drug is therapeutically efficient. Except
we have learned a long long time ago that
there is a possibility that the
improvement in the patient's condition
had nothing to do with the drug itself.
There is always a possibility such as improved
nutrition, the body's natural healing ability,
improved climate, and many other things. So
How do you make sure that these unaccounted factors unaccounted effects don't enter
the picture?
Well, you organize the so-called
controlled trial. So what do you do? You
take two groups of patients, similar
groups. The idea is that they are
statistically equivalent: they suffer
from the same condition, of pretty much
the same age and whatever is
important statistically. You take two
groups of patients. One group received
the drug. The other one doesn't receive
anything. So this will be the control
group. And if there is a notable
improvement in the first group greater
than the improvement in the second group,
you say that the drug is therapeutically
efficient. Except that there might be something
else. Am I missing something?
(Student) "The placebo effect." (Hakob) The placebo effect! What's placebo effect?
Placebo effect is that sometimes the improvement in a medical condition can be due to the
fact that the patient is psychologically
predisposed towards the improvement so
sometimes we know that when patients
know they undergo treatment they showed
signs of improvement and this
improvement may or may not be actually
connected to the pill itself. So what do
we do to make sure that it's not because
of the placebo effect? That it's actually
the result of the drug itself? What do we
do? Well, we organize the so-called blind
trial. We organize a blind trial. Again we
have two groups of patients. This one the,
first one, the active group receives the
actual pill. The other group receives
fake pills, the placebos. The important part of this
whole experiment is that we'll make sure
that they don't about it. In this setup,
we track the progress. If the improvement
in the first group is great than in the
second group, we conclude that the drug
is therapeutically efficient. Am I missing
something here? Can this test be
further improved? (Student) "You think you can ramp
it up by making it a double-blind study."
(Hakob) Why would you do that? (Student) "If someone
is administering the pill but they know
that it's fake they might give up subtle
clues that they're unconscious of and that
might tip off the
testing people." (Hakob) Very good! This is called
experimenter's bias. When people who are
in the immediate contact with patients,
if they are aware which group is which,
they may subconsciously give clues.
Researchers are naturally predisposed
towards getting positive results. We know
this. Because there are mortgages at stake.
Right? We have to get actual results. So what do you
do to make sure that this experimentier's bias
doesn't enter the picture? What do you do?
Just as Stephanie suggests, you have
to make sure that your trial is double
blind. Two groups of patients this time. but
you make sure that none of the
researchers who are in actual contact with
patients, none of them, knows which group
is which. They have to be blinded to this.
Here is a placebo but the researchers
don't know about it. If the improvement
in the first group is greater than the
impermanence second group, we conclude
that the drug is therapeutically efficient.  I'm
pretty sure for many of you this. It is
common knowledge. What I want you to do
now is to think of this whole
development from the logical standpoint.
Here we are going to have accepted theories, the
theories that we believe to be the best
descriptions of the world, everything
that we accept that the moment. And here
we are going to have our methods, our
requirements, our implicit expectations, the
criteria that we employ in testing our
theories. OK? Now, our initial
requirement was something along the
lines of the hypothetico-deductive method. The
requirement was a hypothesis is
acceptable if some of its novel
predictions are confirmed. In our case,
what was the hypothesis? The hypothesis
was that "X-antidepressant is
effective in alleviating depression". This
was the hypothesis under test. And we
were trying to see whether this hypothesis
actually works. So what were we
doing? Following the requirements of
the hypothetico-deductive method.
This was our initial attitude. What happened
next? We discovered that sometimes the
improvement of the condition can have
nothing to do with the drug itself.
It can be due to many other things such as
unaccounted effects. The moment we
discovered this, we changed our implicit
expectations. We arrived at the idea of
the control trial. So the moment you learn
that the human body may show actual
improvement in a medical condition due to
improved nutrition or improved climate or
anything, the moment you learn that, you
understand that the simple one group
testing is not good enough.
You change your expectations. You switch
to control trials. After that you discover
placebo effect. Once you discover the
placebo effect, once you realize that the
improvement may be due to the patient's
psychological expectations, you switch to
a single blind. And finally the moment
you discover that there is such a thing
as experimenter's bias - that researchers
involved in a trial can give
subconscious cues which made bias the
patient -  the moment you realize that, you
arrive at the double blind method which
says the drug's efficacy should be shown
in a trial of forestall the chance of
unaccounted effects, placebo effects and
experimenter's bias. In the most simple
terms, we have changes in methods which
are due to changes in accepted theories.
Is this clear what's going on here? So if
anyone told you "why is it that you don't
really employed the controlled trial method?
and why is it that you employ a
double-blind trial method? You say "well,
because we have experimenter's bias, we
have placebo effect. It's not a
random choice. Is it? The moment you
accept those effects, the choice of the
method is no longer around. All agree?
I'm going to give you another example.
Let's say my initial requirement is
along the lines of hypothetico-
deductivism. I say the hypothesis is
acceptable if his predictions are
confirmed by experimental observations.
But we also know that we have this
internal tendency to forge the results
of experiments and observations. For many
different reasons I could mention:
grant money running out and
all the other things, you just want to produce
positive results. Not everyone is guilty
but we have that tendency. So what do you
do to forestall the chance of this
entering the picture. There's no way you
can have an absolute guarantee, but what
do you do to at least protect yourself
to a certain degree? Is there anything
that can be done here? we want to make
sure that what they do is actually
repeatable. That's the idea.
It has to be repeatable. The hypothesis is
acceptable if its predictions are
confirmed in a repeatable experiment or
observation. So if I have an hypothesis, let's say
my hypothesis is that there are very
tiny angels within quarks ... why not? ...
tiny little angels such that they only
manifest themselves on October 1st
12:30 Eastern time, once ever. And I
was lucky enough to be there to observe them.
Here the report, 80-page report,
with all the photographs and everything.
You say, "well, this this is not really
repeatable! OK, at this point I know
what you are thinking: "Well, what about
the hypothetico-deductive method itself?"
you may get an impression that there is
some sort of a hierarchical methods and
the foundation of that hierarchy from which you
have the hypothetico-deductive method,
which appears to be unchangeable. What
about hypothetico-deductive method?
It is also based on some assumptions. What
are the assumptions? The first assumption
is the idea of complexity.
This is the idea that the world as it
appears in observations and experiments
is a product of some more fundamental
inner mechanism. So we believe there are
things that are not directly observable.
This is an assumption implicit in all of
the contemporary science. We believe that
not everything is observable. We believe,
for instance, in the existence of particles,
forces or interractions. Nobody's ever
observed them with the naked eye.
You understand that? We use instruments
to observe them and instruments are based on
theories therefore we say well it's OK
to hypothesize the existence of things
which are not directly observable. So we
believe that the world is more complex
than it appears in naked eye
observations. There are layers and layers
and layers of complexity out there.
Basically this is the old idea that
there is more to the world that meets the
eye. And I think it's safe to say that
this idea is nowadays implicit in the
contemporary science. Can we all agree on this?
Very good! The second assumption is
the assumption that any phenomenon
can be given many different contrasting
explanations after the fact.
It's called post hoc explanations.
Post hoc explanations are always possible.
This is the idea that everyone
might be smart after the fact.
Think: astrology. Suppose you are a Cancer.
Cancers are supposed to be very family-oriented,
very friendly. In a list of priorities
career should not be in the first place
if you're really a Cancer
according to traditional astrology.
Family, children ... those things should be
number one. And yet I'm 35 years old and
I'm not married and not not even close.
And you are not going to find two astrologers
who provide the same explanation.
But everybody is smart after the fact! Believe
me, they will come up with all sorts of
explanations. May be it has to do with
the position of Mercury at the time of
my birth or Venus or whatever, I don't
know. But they will be able to provide
different explanations. A more
scientific case: a falling apple.
We see that this very basic case could be
explained by the Aristotelian physics,
the Newtonian physics, by the Relativistic
physics. The same falling apple. Can all
agree that the same phenomenon can be
given more than one explanation? Yes!
Therefore we have to understand that
everyone might be smart after the fact.
So what do you do to make sure that
post hoc explanations
don't crowd your science? That you don't
get too many Post doc explanations? What do
you do? "Well", you say, "it's OK to
hypothesize the existence of particles,
forces, superstrings ... whatever as long as
the hypothesis itself predicts something
novel, something hitherto unobserved. So
it's not just an attempt to come up with
some sort of an explanation of the
available data, but it also predicts
something that has not yet been observed.
Again there is no guarantee but at least
this way we protect ourselves from
forged explanations, from cooked up
explanations, post facto explanations.
When Einstein was trying to convince the
scientific community that there is
actually the space-time continuum that
is capable of curving, a seemingly
ridiculous idea, he only managed to do
that when one of the predictions of the
theory turned out to be true:
the prediction of light-bending, the light
coming from distant stars actually gets
bent when it passes near massive objects,
a phenomenon never observed before.
First, we wouldn't tolerate unobservables if
we thought that the world was composed
only of what is immediately observable.
Right? If you thought that the world is
basically made of colorus and
smells and tastes, you wouldn't
really tolerate unobservables, would you?
The moment somebody came here and said
"I believe in the existence of
molecules." You will say: "It's just ridiculous!
It has no smells and colours!" The reason why you
tolerate that is because you believe that
the world contains layers and layers of
complexity. And we wouldn't need any
novel predictions if there weren't the
risk of post hoc explanations,
if any phenomenon only allows one and
only one explanation. You wouldn't
need to confirm novel predictions. So you
see how we arrived at the hypothetico-
deductive method? The moment we accept
those fundamental premises -  the principle
of complexity and post hoc explanations - we
arrive at the hypothetico-deductive method.
One thing we have to appreciate. 
Since those principles are changeable,
these are synthetic propositions.
There is nothing
self-evident, so therefore these principles
are changeable. The world could have been
otherwise. Since these principles are
changeable so is the hypothetico-
deductive method. Suppose, for the sake of
argument, hundred years from now somebody
comes up with the theory which tries to
convince us that the world is actually
made of only sensation - smells, tastes
and everything else we thought
we've seen. Molecules and atoms and
quarks and leptons in all other things
are just an illusions. In reality there are
just smells, tastes and nothing more.
It's not very believable, given the current
state of affairs. But can you imagine
such a theory? Now suppose, for the sake
of argument, somebody comes up with that
theory, there is only one way it can be
accepted when it provides confirmed
novel predictions. And suppose, for the sake of
argument, that it does provide confirm novel
predictions and becomes accepted.
Scientists on the 22nd century
believe that only smells, colours, tastes,
sounds, and nothing more. In that world you
wouldn't be allowed to hypothesize any
further. You won't be allowed to hypothesize
any internal structure because this will
be the end of it, this would be, well, the
world is not really complex, the world is
just as it appears on observations.
That's it! You see, your method would
change again. We don't have to
hypothesize. We just look back in the
history of science,
400 years ago at the Aristotelian-
Medieval method which has nothing to do with
confirmed novel predictions. It was based on
two assumptions. The first is the idea
that everything in the world has a
nature. And the nature is that one property that
makes the thing what it is. So let's say
you have an acorn. What is the nature of
an acorn? It's the capacity to grow and
become an oak tree. That's what defines
an acorn. So if you have an acorn that
is not capable of growing and becoming
an oak tree, it's not much of an acorn, is it?
True by definition. That's what
characterizes an acorn. How about lion cubs?
What's the nature of little lions?
Well, probably to grow and becomes full-fleged
lions. That's what they do. And finally
what is the nature of a human being?
Socrates here, typical example of human
being. So what is it that characterizes
a human being?
Capacity of reason: arriving one set of
propositions to another set of
propositions, rational thinking. So this was
the idea: everything has a nature.
Second assumption was that an
experienced person, a person who is
actually experienced with certain types
of things, is in a good position to have
a correct intuition as to the nature of
the thing. So an experienced person can
actually grasp the nature of a thing,
under studyt. In this case, Socrates can say that the
natural an acorn is its capacity to grow
and become an oak tree and the nature of lion
cubs is to grow and become a full-fledged
lion. And the same applies to everything.
Basically if you want to know what
a thing is, you go to an experienced person
because that person would be in a
position to have an educated intuition.
This is not a blind intuition, OK?
This is an educated guess. If you accept these
two assumptions, there is only one step
to the Aristotelian method: a proposition
is acceptable either if it's grasped by
an experienced person who grasps it intuitively or
if it's something that is strictly deducible
from other propositions. Again
as we see here, our expectations here
follow from our beliefs about the world.
Is this clear? Let's sum it up.
Methods becomes employed only when it is
deducible from other employed
methods and accepted theories of the
time. So when is it that we employ
certain methods? When it is deducible
from our accepted theories and maybe
some other methods. This, I believe, is a
general pattern. Give me any case of
method employment and I'll be able to
show you that it was based on some tacit
or explicit assumptions of that
particular community. Any method you want,
hypothetico-deductive method or
Aristotelian-Medieval method.
Think of any method you want, and
that method, will be a deductive
consequence of the theories and other
methods accepted at the time. And because
this is a universal feature of science,
we call this a law of scientific change.
It even has a number: it is  the 3rd
Law of Scientific Change. This is the
law of method employment.
What are the other laws?
Let's start with the first law: an
element of the mosaic maintains its
state in the most like unless replaced
by some other elements. I'm going to explain.
The 2nd law: in order to become accepted
into the mosaic, a theory is assessed by the
method actually employed at the time.
The Zeroth Law: at any moment of time, the
elements of he mosaic are compatible with each other.
This is the law of compatibility. It says that
theories are part of the same
mosaic are always compatible! But what makes two theories compatible? To understand
this, we have to appreciate the structure
of a method. When I say method, what do I
mean? Basically a set of requirements
that we employ in theory assessment.
We know this. From the logical point of view a
method can have three different types of
components. It can consist of three
different types of criteria. The first
and most obvious are the acceptance criteria,
a set of criteria employed in deciding
whether theories acceptable. In addition,
there are democratization criteria. These
other criteria that decide whether
a theory is scientific or not.
And finally, in addition to these two,
there's a third type of criteria which
will call compatibility criteria. These
are the criteria that help us decide
whether any two theories are mutually
compatible or incompatible. So this is
what we have. These criteria here we
employ these to tell whether a theory
is scientific or not scientific. The fact
that its scientific doesn't make it
acceptable. We have Superstring theories
which we believe are scientific but are
not accepted.
You understand there's a difference? Right?
The theory maybe scientific but not
necessarily accepted. These criteria here we
employ them to determine
whether scientific theory is to be
accepted.
And finally these ones here we employ
them to determine whether theories are
mutually compatible or incompatible. The
important point is: since methods are
changeable - we know they are - so are the
criteria of compatibility. They are also
changeable. So two theories considered
compatible today may turn out to be
incompatible tomorrow. Even nowadays
our attitude towards compatibility and
incompatibility depends on many
different things. We don't have to really
delve into the history of science to
appreciate this phenomenon. I'm going to
give you a simple example. Let's go to
formal science, We are in the field of
mathematics and the famous Four Colour
Theorem. This is the theorem that says that any
planes separated into contiguous regions
requires no more than four distinct
colours to colour all the regions so that
no two adjacent regions have the same color.
Basically the idea is that four colors are
sufficient to color any map. I'm going to
give you a hypothetical case: what would
happen if we came across a map that is
shown to require more than four colors
to color? Suppose there is a map and the
requires five distinct colors to color,
like that. Suppose this were actually
the case - just for the record this is not
actually the case - it is possible to
colour any map with four colours. This was one of
the suggested anomalies, one of the
suggested refutations. But suppose for
the sake of argument that we study this
case and really there is no way to color
it by using only four colors, and
it requires at least five. How would you
react? If this were really shown to be
the case, then we will declare the four
colour theorem void and the deduction
will be void. We know that the deduction
is not straightforward. We used a very
complex computer algorithm to prove it
in the first place. So probably you say, "Well,
it was probably something wrong in the
algorithm or in the deduction itself." So this
one instance would be sufficient for us
to reject the theorem. And the reason why
we do this is because in formal science
we are inconsistency intolerant. There is
no tolerance towards inconsistencies
in formal science.
Why is that? Well, because in formal
science we believe that every established
proposition is absolutely true.
The moment you believe that everything you
have must be absolutely true
- in formal science we know that that's
the case - then one counter example is
sufficient to question all the
deductions. The moment you establish that
the theorem has to go. Let's take another
example. This time from empirical science.
Kepler's First Law: the trajectory of
every planet orbiting a star is an
ellipse with the star at one of the two foci.
Basically the idea is that every planet revolves in an ellipse.
Suppose, for the sake of argument,
that we came across a planet that does
not revolve in an ellipse. Suppose we discovered
a planet which has a weird 8-shape
trajectory. How would you react to this?
What would you say? What's your natural instinct?
(Student) "Since it's not formal science, I would
check if there any other unexplained
variables that we do not look at.
For example, there might be something in that
hole there is closing in."
(Hakob) He is right. We're not going to rush to rewrite the
textbooks immediately and reject the
Kepler's Law. We are going first and foremost
to question our observations, to question our
calculations. We are going to come up with all
sorts of hypotheses. May be there is a
second star which we haven't yet
discovered or maybe there's a small
tiny black hole. God knows what! That
could be many many different things.
We're not going to reject the law. Why is
this? Because in empirical science
we are inconsistency tolerant. So what makes us inconsistency
tolerant in empirical science?
We seem to be saying: two analytic propositions are compatible
only when they are mutually consistent.
So if you have two propositions in formal
science and they are inconsistent,
there's a contradiction, that they cannot
be compatible. You cannot accept
both. You have to choose.
Either the four colour theorem or the anomaly. On
the other hand, two synthetic propositions in empirical science
might be compatible even when they are
mutually inconsistent, even when there is
a formal contradiction, just like in the
case of the 8-shaped trajectory and the general law.
The two contradict each other. From a logical
perspective you cannot accept both and
yet we do. Any empirical theory you take 
has a whole bunch of anomalies which we
accept and yet we do not think that
those anomalies are sufficient to lead
to the rejection of the theory. Why is
that? Why is this discrepancy? In formal
science we are intolerant towards
inconsistencies but in empirical science we
are tolerant. Why is this?
Think of it this way: if you believe that
all your accepted theories are
absolutely true, then you understand the
two propositions that are inconsistent
cannot be absolutely true at the same
time. We understand this. So contradictory
propositions cannot be both true at the
same time. In empirical science, we do not
believe that our propositions are
strictly speaking true, right? We believe
that they are at best
quasi-true, they are approximations.
Think of it: the moment that you
understand that your empirical theories
are not really perfect, what do you? OK,
this theory is not perfect and that theory is
not perfect.  It's possible for them to be
contradictory within this theory. It is
totally fine, right? Because none of these
theory is perfect, you see? So this is the
idea of fallibility. Synthetic propositions
can be only quasi-true. This is what we
believe. They're never absolutely true.
They are only approximation. Only analytic
propositions can be strictly true. You put those two
together and you arrive at this criteria
of compatibility. Some time ago I was
talking to a former girlfriend with whom I
still keep in touch - this is a very very
former former girlfriend - and she
confessed, she said, "Well, I'm dating
two different guys at the same time." I
said, "Yeah ...moral questions aside,
why would you even do that?  That's time consuming and
why would you do that?" She said, "Well,
you know Hakob, if I have a perfect
boyfriend I would stick to that one
perfect boyfriend, but you see none of
the available ones are really perfect so
I take the best of two worlds."
This is very similar to what we do in the
contemporary science. You have quantum physics
and general relativity and, strictly speaking,
they contradict each other.
You know that general relativity is accepted as the
best available description of massive
objects. How massive? Well, macro world and
all the way to the Mega world: planetary
systems, galaxies. Quantum physics on the
other hand, just as the name suggests, is
the best available theory of minute things,
tiny things. So the two theories proved
to be very very good when it comes to
explaining the facts of their own domains.
General relativity is good in its own domain.
Quantum physics is good in its own domain.
Except that sometimes you need to apply
both theories at the same time. Can you think
of an object that requires both theories?
(Student) "Starts, given the fact that
their plasma gas ... "
(Hakob) What happens to the largest possible stars? 
(Student) "Oh, OK, Black holes!"
(Hakob) Singularities within a black hole!
Now a singularity within a black hole
is extremely masive and yet very very
minute so you need both quantum physics
and general relativity to explain that.
The problem is the moment you apply two
theories at the same time, you arrive at
contradictions. So we have a clear-cut
case of two accepted theories being
strictly speaking in contradiction with
each other and yet we accept the two theories
because we understand that none of the
accepted theories is perfect.
OK? That doesn't justify the moral
decision of dating two guys at the same time!
Question? (Student) "You are saying that both
of those are contradictory. But do we
have an answer, a truth, to the contradiction?"
(Hakob) No, we do not have! We have a
theory that we pursue, the Superstring theory,
which we hope will solve some of
the contradictions. But at the moment we
keep accepting both of those theories
despite the fact that they contradict.
And this is the key idea of the Zeroth
Law. If you think about it,
what the Zeroth Law tells you that compatibility
should not be confused with consistency.
They may or may not be consistent. By the
way this law is proposed by
a good friend of mine who used to be one of my
students who is the author of
this law. Initially I thought every
theory should be consistent with every
other theory but then you know little
bit of history of science it turns out
not to be the case. And he modified the
Zeroth Law and brought the law to its
current form. This is what he did. The 2nd
law: in order to become accepted into the
mosaic, a theory is assessed by the method
actually employed at the time. This is basically
a tautology. This is something that
follows from the definition of employed method.
So when I say that in order to
become accepted into the mosaic,
a theory must satisfy the requirements of the
method of the time, not the methods of
the past but the current method, what am
I saying? If you want to convince the
community, you have to meet their
implicit expectations which is the same
as to say you have to convince the
community.
This is a tautology. We only need this law in our
future deductions and that's what we're
going do. This one on the other hand -
this is the law of
scientific inertia. This is the law that
says that once in the mosaic, the theory or method stays
in the mosaic unless replaced by some
other elements. Now let's see what
follows from this. If you take this as
your starting point, then you can say
that an accepted theory remains accepted
unless replaced by other theories.
This is the 1st law for theories. Then you
take the zeroth law, the law of
compatibility. Put them together and you
arrive at theory rejection. Let's
go step by step.
You haven't accepted a theory. It remains
in the mosaic. It doesn't need anything else
to remain there. It's just scientific inertia.
How can it be replaced?
How can it be pushed out of the mosaic? There
is only one way. And that way
suggested by the Zeroth Law, the Law of
Compatibility: there must be some other
theory that is incompatible with this
theory that gets into the mosaic,
and pushes the previous theory out of the
mosaic. That's how theories becomes rejected.
Let's consider an hypothetical case first.
You have theory and you have method.
Let's say you have three theories that
are Zeroth Law compatible - that's why they're
part of the same mosaic - and then you
have a contender theory, theory 4 that has
just been proposed and not part of the mosaic.
Question: should this new theory be
compatible with every other theory in the mosaic?
It's not in the mosaic but should it be compatible
with each and every element of them?
At this moment, not necessarily. It's a
new theory.  Chances are it comes to
replace one of the theories in the mosaic.
So it may turn out that it is
incompatible with theory 1, let's say for the
sake of argument. How does it get into the mosaic?
By the 2nd law it must satisfy the
requirements of the method of the time.
So the moment it satisfies the
requirements of the currently employed
method, it becomes accepted into the
mosaic. And this theory here, which was
incompatible with the new theory, becomes
rejected. And the compatibility is maintained.
Let's take an actual historical
case. For Aristotelian physics,
the Earth is sphere and that it has to be in the
center of the universe (Geocentrism).
In the center and being spherical
- both of these propositions
follow from the Aristotelian physics
and the method of the time was
Aristotelian-Medieval method. Then we
have the Cartesian physics which had to satisfy
the requirements of the method of the
time. And that's what it did.
When it became accepted, it was incompatible
with the laws of the Aristotelian physics.
Therefore the Aristotelian physics would
have to go. It was also incompatible with
geocentrism because it follows from the
Cartesian physics that planets revolve
around stars, not the other way around,
and so this had to go. It was replaced by
heliocentrism. But this one -  this one
remained in a mosaic because it followed
from the Cartesian physics - the Earth
is spherical -  that didn't change. Basically
we take each and every proposition
individually and see whether the new
theory is compatible or incompatible.
with those things. And everything that is
incompatible is being cut out of the mosaic.
OK? Another interesting theorem
is what we call the Contextual
Appraisal Theorem. On the one hand,
an accepted theory remains accepted unless
replaced by other theories (the Law of Inertia)
which tells us
that theory is only assessed when it
tries to enter into the mosaic, not when
it is already in the mosaic. So when you
come across people who try to convince
you that your accepted theories are
no good, the only thing you to have to say
is, "Well, it's already in the mosaic.
Do you have any replacement?
Do you have anything better? What you want me
to do? You want me to abandon this theory and
remain with nothing? Is that what you want?"
Now the 2nd law tells us that
in order to become accepted, the theory must
satisfy the actual requirements of the
community. You put the two together and
it is obvious that the theory assessment
is an appraisal of the proposed
modification. So basically what we assess
- we have a new theory - what does this new
theory do?  It, in a sense, proposes a
modification to the mosaic, right? That's
what a new theory does. It says, "Well, I'm
going to enter into the mosaic. Assess that!
Assess that modification!" That's what
a theory assessment is all about. And t
happens with the method employed at the
time. Not the method of the past, not some
ideal method that you have in mind, but
by the actual expectations of the
community of the time. They say, "Well, Hakob,
this is a very simple theorem
called Contextual Appraisal, meaning that
you have to take the historical context into
account." But why would anyone bother
proposing this theorem? I would have
never bothered if it hadn't been for many
mistakes in both popular literature and
unfortunately also in professional literature.
I'm going to give you a few examples. Take a
timeline, 1945. This is roughly the year
when the so-called modern evolutionary
synthesis was accepted.
You all know the theory. This is the
theory, OK? ... and it goes all the way down.
So this is a theory that we currently accept
as a scientific community.
Now you know what happens
these days? These days we have the
so-called creationists which use the
incompleteness of the fossil record to
criticize the evolutionary theory.
You all know the story.
Intelligent design: nowadays they're not
allowed to use the term "creationism"  so they
changed the name to "intelligent design",
essentially the same idea.
What is their major argument? What is it that
they're trying to say? "Well,
the fossil record, evolutionary tree, species
living and extinct, there are serious gaps."
If you understand the
Contextual Appraisal Theorem, you also
understand why this is wrong. Let's have a look.
This is what the theory says: Mankind and
all life on the earth were created by
God within the last ten thousand years
as distinct fixed kinds, ex nihilo
(ex nihilo means "out of nothing").
This is the classical version of the
theory. I believe nowadays there's not many
people who subscribe to this particular
version. But let's stick to this one for
the sake of argument. So this is the
Creator here. Everything was created by
the Creator ex nihilo as fixed species and no
evolution! They also say that all those fossils
that we happen to find in geological
strata were
deposited by God during a flood which
covered the entire earth. You know,
to make the life of scientists more fun, I guess?
What else will we do without fossils?
What's wrong here is their
conception can never become accepted
unless it manages to satisfy the
contemporary requirements. What are those
requirements?
Hypothetico-deductive method and confirmed novel
predictions. So this negative criticism
doesn't do anything. They do not
understand that all theory assessment is contextual.
The mere fact that you manage
to come up with some sort of a post facto
explanation of all those
phenomenon that we observed is not
enough. How do you make this theory accepted?
Well, there's only one way: satisfy the
requirements of the time. I'm not saying
they have much of a chance. They don't.
But the only chance they have is to
stick to the contemporary requirements
and understand that their theorr is not
accepted. There is an accepted theory.
You want to convince the community? Well,
convince the community! It's almost a
tautology! Let's take another case.
Going back in time,
1610, heliocentric astronomy wasn't 
accepted as one of the proposed theories.
This here was one of the novel
predictions of the theory, you remember
the case? Popular science mythology
tells us that when the prediction of
this theory was observationally confirmed. From that
moment on, this theory was advantageous
to the then accepted geocentric theory. This is
what your popular myth tries to
convince you. When you read popular
literature, why is it that people say
that Galileo was treated unjustly? 
The reason is that those commentators of
popular science authors take the
contemporary method of science,
hypothetico-deductive method, and appraise
that case of the past with the contemporary
method of science and say Galileo's
theory was advantageous because it had
confirmed novel predictions. It had confirmed
novel predictions indeed! You see, phases of
Venus was a confirmed novel prediction.
Nobody had ever observed phases of Venus
before they were observed by Galileo. 
If they only employed the contemporary
hypothetico-deductive method. Galileo's theory - 
Copernicus's theory essentially - would be
advantageous. But the popular myth forgets
that the method of the time
had nothing to do with confirmed novel
predictions. It was the Aristotelian-
Medieval method that was completely
different. People didn't expect novel
predictions. People didn't expect confirmed 
novel predictions. What they expected was
intuitive truth, and this truth was
anything but intuitive. So essentially what
they do is to anachronistically apply the
hypothetico-deductive method here -
our contemporary criteria to the 
historical case. This is a typical case of
anachronism: take your contemporary
criteria, apply to the science of the past,
and declare those guys arrogant and
ignorant and dogmatic. They were
anything but ignorant, anything but 
dogmatic if you study the actual
historical records of the time and you read
the actual debates when Galileo and the
Aristotelian clergy, you will realize that
many of the things those guys were saying
actually made total sense! Those guys
were saying: "You know what, your theory is
not intuitive. Your theory contradicts the 
foundation of our physics, the Aristotelian
physics. So what do you do? You want us to
reject the whole system of the world?
You have any alternative?" Again, what's
forgotten here, what's neglected here, is
the contextual nature of appraisal. 
Appraisal never happens in a vacuum.
It always happens in specific historical
circumstances. And these circumstances were
such that Galileo's theory, the heliocentric
theory, was not advantageous to the then
accepted geocentric theory. Is it clear? Good! 
Now this theorem here I'm going to deduce now
is, if not the cornerstone, at least 
one of the most important
achievements of the theory that we
propose. 2nd Law tells you that you have
to satisfy the actual expectations. What
happens when you have two theories,
incompatible contender theories
proposed at the same time and both
manage to satisfy the requirements of
the method of the time. Let's say both
theories got confirmed with the same
observation, same experiment.
Both theories predict pretty much the same
things. We have two completely
different theories with
the same predictions and they both
manage to convince the community that
they're equally good.
What happens? The 2nd Law tells us what's
going to happen! Both will be accepted.
But, Hakob, you told us that if two theories are 
incompatible, how can they be simultaneously accepted in
the same mosaic? The Zeroth Law 
tells us that this cannot happen.
At ever moment of time, the mosaic must be
compatible. All the elements must be
compatible. So what happens here? What
happens here is the mosaic splits. When two
incompatible theories meet the
requirements of the method simultaneously,
the mosaic splits in two. If you have two theories 
in the mosaic, both incompatible, this leads to
a mosaic split. We have historical
cases when you had one community in one
part of the world teaching one set of theories and
another community in another part of the
world teaching another set of theories.
We even had cases went to neighboring
departments within the same university
taught completely different sets of theories.
So these things happen. It is
what we call mosaic split.
The phenomenon is commonplace in the history
of science. I'm going to give you the
classical case. This is probably the most
difficult case to be tackled by any
theory of scientific change. This is 
the so-called scientific revolution,
the transition from the Aristotelian-
Medieval system of theories to those of
Descartes and Newton. 1680, the late 17th
century, you have the Aristotelian system
of theories. Now, how could this system
of theories be overthrown? What would you have to
do in order to have a chance?  
(Student) "What we can do is to find
competing theories  intuitively confirmable." 
(Hakob) You know the rules of the game!
If you're in the 17th century, the only
way to convince our community is to
make sure that you have a comprehensive
set of theories which appear even more
intuitively true than the theories accepted.
So you have to satisfy the
requirements of the Aristotelian-
Medieval method here. So these are the
requirements. One truth about this
requirement is that this requirement is
so vague that it is possible for many
different theories to simultaneously
satisfy that requirement!
We are all in the 21st century, and we know
that what appears to be intuitively true
to me may or may not appear intuitively
true to you, right? Now what's common
sense for you may or may not be common
sense to me. As a result, by the end of
the 17th century, two theories, Newton's
and Descartes's are shown to be
intuitively true. You had two theories
that simultaneously satisfied the
requirements of the time. And as a result
this led to the existence of two
different communities, one accepting the
Cartesian set of theories and another one
accepting the Newtonian set of theories. 
On the timeline: this is your Newtonian theory,
laws of gravity, Newton's laws, and from 
those laws he was trying to deduce as
many theorems as possible. If you ever
looked at Principia Mathematica, the famous
book in which his theories were presented - 
he shows that the laws make sense
and after that he deduces a huge
axiomatic deductive system. Among other
things:  the orbit of every planet
must be an ellipse and every planet
is oblate spheroid flattened towards poles 
and many, many other things.
His system appealed to
the community because it was based on
seemingly intuitive axioms and deduced 
theorems. And if you look at the structure
- forget about the content, forget about
what he was trying to say -  look at the
structure, he was trying to create a
theory that would appeal not only to his
contemporary fellow physicists who
didn't care about the Aristotelian stuff,
but also appeal to the Aristotelians. 
The same can be said about
Descartes: a similar system, completely
different content but similar
structure. You have seemingly intuitive
axioms and deduced theorems. Again this
may be considered as an attempt to
satisfy the requirements of the
community of the time. The content is different
but the two theories are trying to accomplish
the same thing. They are trying to
convince the community what Galileo failed.
I'm going to take this Theory-Method Diagram
and flip it like that. All the way
until the end of the 17th century,
you had the Aristotelian-Medieval theories
and the Aristotelian method. That was a
deductive consequence of those theories
by the 3rd law, OK?
What happened by the end of the 17th
century: two theories managed to satisfy
those requirements and a mosaic split 
took place. Here, the early 1700's
all the way until 1740, you had
different communities in Britain and
on the Continent. On the Continent, for the
most part, they accepted the theory of
Descartes and his followers who were
Cartesians. So if you went to Paris
University around 1720 for instance, you
would see that they actually studied
Cartesian physics. If you went to
England in the same time period you would see
that they studied Newtonian physics. 
Voltaire spent a number years in England
in the 1720's and he wrote his famous
English Letters. Some of those letters
(Letters 15 and 16)
specifically referred to these
differences between the Newtonian worldview
and the Cartesian worldview. As a Frenchman,
he was an educated Cartesian. But by the
time he went to England and came back,
he was no longer Cartesian. He was convinced
that the Newtonian theories were the right one.
The interesting part is how he
compared the two theories.
He said, "Well, here we believe that the 
whole world is a mechanism and everything
happens by actual contact. Those guys over
there across the channel in England
believe that things actually attract
each other from a distance. While we believe
there is no such thing as empty space
and the world is full of things and
everything is actually mechanistic, you know,
clocks, levels, sprints, whatever,
guys over there in England
believe that it's just masses and
attraction. Two completely different worldviews. 
What happened after that? This is the
key part: the moment you accept any of
the two theories, Cartesian or Newtonian,
it doesn't matter, your fundamental method
of science undergoes a transition!
Now I'm going to show you how you arrive at 
the hypothetico-deductive method the moment
you accept any one of these two theories.
At this moment you understand why these
two theories became accepted. Now what
remains to be understood is
how we arrive at the hypothetico-
deductive method the moment we accept any of
these theories. This is what I'm going to show. 
I'm only going to show the Descartes theory but the same
deduction also takes place in the Newtonian 
theory which I will talk about in Lecture 9
when we get to the Newtonian world veiw. 
Today, just Descartes. A fundamental principle
of his theory is that matter is extension. We've 
covered this. Everything out there,
everything is material, has only one
attribute which is the capacity to occupy
space. If you accept this, it follows that
any phenomenon can be produced by an
infinite number of different arrangements
of parts. I'm going to explain that.
Let's take three watches absolutely identical
from the outside. So the same phenomenon.
You can trust me - I just copied and pasted the
same image. So absolutely identical from the
outside. And yet it is conceivable they
may have completely different
arrangements of parts.
This is the idea. You have to appreciate
that the same effect upon your senses
can be produced by a different
arrangement of parts inside.
Another thing that we have to take into account 
 is that all other qualities like colour,
taste, weight ... all other qualities except
extension, all other qualities result
from the combination of these material
parts. So there are no actual colours
out there, there are no actual smells out
there, there are no actual tastes out there.
It's only moving parts, right?
That's the only thing you have.
So all the effects upon your senses are the 
products of the combination of different parts.
Colours, for instance, let's say the white
colour, would be some combination and
black color would be another combination
of parts, right? If you accept this,
it is possible to provide an infinite
number of different post hoc
explanations to everything, right? You get
the same phenomenon and you sit down to
hypothesize “OK, what could have possibly
produce this phenomenon?" I can come up
with my hypothesis, you can come up with
your hypothesis, and we can have an
infinite number of hypotheses. This
brings us to the idea that everyone
might be smart after the fact. You see
the deduction here? Very good!
And if you accept this, then you also
accept implicitly the idea that the
world is more complex than it appears in
observation. The world is not just
about smells and colours. There are
other things: particles and parts and there
can be different kinds of arrangements,
there can be anything, as long as they're
materials a occupy space. The rest is
obvious: you have these two principles,
you put them together, and your arrive at the
hypothetico-deductive method. This is
how Cartesians became hypothetico-
deductivists. Descartes himself knew this,
although he didn't quite take that step.
Descartes was never engaged in actual
observations and experiments. He was a
system creator. But he says in the very
system. "Well, although I am in a
position to deduce many of the theorems
of my system, when it comes to specific
details, let's say the explanation of
magnetism or gravity,
you cannot deduce these things, you
have to hypothesize these things,
and then you have to test your hypotheses
experimentally. The second generation of
Cartesians, in particular one Christiaan 
Huygens from the Dutch Republic,
Netherlands,
(Hakob pronounces Huygens's last name)
It's easier for me because I have the
same sound in my last name Barseghyan,
the same "gh". So Christiaan Huygens 
understood that this was the way to do science.
This is what we have: we have accepted
theories, and by the 3rd law the
new method here became employed because it
was a logical consequence of our
accepted theories. The moment you accept 
these theories, your fundamental method
of validation changes. And after that - you
know the rest of the story - in the 1740
one of the predictions of Newton's theory
was confirmed and that's how we had
Newton's theory accepted on the continent as well.
You remember the oblate spheroid hypothesis?
It was already tested by the hypothetico- 
deductive method. So scientists around
the 1730's already expected
confirmed novel predictions. That's
the reason why they organized those two
expeditions in the first place. Why else
would they bother? You see that's a good
indication that they expected confirm novel
predictions. They wanted to test, unlike
their peers from fifty years ago.
You see the transition? See how it
happened? Magnificent, isn't it?
And yet completely rational, completely
logical. There is no random choice of
methods. You don't get to randomly pick
your criteria.
Very good! Let's sum up. These are the
four laws - three of the laws are my creation
and one of them is Rory's creation and we
have a whole bunch of people who suggested
many interesting theorems and modifications
to theorems. At this moment, if I zoom out,
these are the laws. This is the system we
have at the moment. You don't have to go
into detail but these are the theorems
that follow. So we have a whole
full-fledged theory of scientific change
that explains things such as theory acceptance,
method employment, theory objection, 
mosaic split and the role of socio-cultural
factors ... many many different interesting
things. Go to our diagram: should we
really deny that there is no universal
method of science? No! I think it's clear
that there is no fixed method of science,
so this argument stands. It is just not vital
as we've seen the fact that there is no
fixed method of science doesn't mean that you
cannot have a theory on how these methods
change. As for this argument, it's just
not true!
We've seen here that all cases of
scientific change seem to obey a
certain logic, a certain pattern. 
This is essentially I argue for and
this is the reason why I believe that
scientific change is a rational,
law-governed process. Now, we have
established that the game of science obeys
certain rules, certain laws. Whether our
laws are correct or not, we don't know,
but I can say that there are certain
patterns. We know that! But this doesn't
mean that we actually progress towards
truth. So the fact that there are rules
doesn't guarantee that we are actually
getting better in our explanations of
the world.
Yes, we may or may not be playing by the
rule book, but what makes us think that
playing by the rule book is actually going to
get us any closer to a more correct
description of reality? so for next time:
does science reveal anything about the
world as it is? In other words, is there
such a thing as scientific progress?
I'm going to cover this next time. For today,
thank you very much! Thank you!
