Video summary
Pierre-Simon Laplace's 1814 essay, *A Philosophical Essay on Probabilities*, represents a pivotal shift from deductive reasoning to inductive probability, offering a rigorous framework for navigating a complex world where perfect knowledge is unattainable. By formalizing the transition from axioms to observations, Laplace introduced the concept of "good judgment" as a calculated approach to truth that surpasses mere intuition or common sense. This probabilistic mindset extends deeply into moral philosophy and legal systems, suggesting that laws should function as probabilistic thresholds rather than relying on binary absolutes; for instance, a conviction is justified only when the probability of guilt exceeds a high standard, while appeals processes serve to aggregate diverse judgments and minimize error rates through the wisdom of the crowd.
The essay also critically examines human cognitive illusions, anticipating modern concepts like the gambler's fallacy, confirmation bias, and familiarity bias before these terms were coined. Laplace argued that people often validate pre-existing beliefs by cherry-picking evidence or attributing patterns to non-existent causes, such as numerology or astrology, which violates the principle of Occam's Razor in favor of simpler, random explanations. A poignant historical example illustrates the danger of failing to apply Bayesian updating correctly: during the Dreyfus Affair, anti-Semitic observers interpreted a lack of evidence against Alfred Dreyfus not as proof of his innocence, but as confirmation of his guilt, demonstrating how prejudice distorts the logical process of updating beliefs based on new data.
Practicing objective judgment is inherently difficult because humans naturally seek loopholes to support their existing views through motivated reasoning, making it essential to pre-commit to specific predictions before encountering new evidence. By explicitly assigning probabilities to outcomes and forcing oneself to consider how one's beliefs would change if the opposite evidence were observed, individuals can detect and correct for confirmation bias rather than engaging in self-deception. This disciplined approach is not merely theoretical; it has real-world implications for technology and society, as seen in recent research on facial recognition algorithms that revealed significant biases against certain demographics. Such empirical findings have already led to moratoriums on deploying these systems by major tech companies for police and military use, highlighting the urgent need to integrate probabilistic thinking with moral philosophy to address AI bias and ensure ethical applications of technology.
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hello everyone uh today we'll discuss
the philosophical essay on priorities
by piercing this is a very important
essay
because it brings together the theory of
probabilities and
unexpected connections with moral
philosophy ethics epistemology the way
of thinking correctly et cetera
and the the reason why we picked this uh
the anecdote why we picked this text
to read actually was that a few weeks
ago the the statistics community had um
had a controversy or whether to rename a
a a an award an important award in
statistics called after ronald fisher
and people were protesting since fisher
had some eugeniestic and
and racist views and um i was personally
wondering
uh so so some people argued that fisher
in the in the
early 20th century was a man of his
epoch etc and
so i was just personally i was just
thinking that um
there are many thinkers who who had
views that are not necessarily based on
the
the the generally held opinion of their
epoch
or of their culture or of their region
etc
and i thought of laplace because uh he
wrote this essay and i just went to the
essay and
and searched for four key words related
to to race or slavery etc and
and found out that that laplace was
arguing that some
commonality and frequently held beliefs
that if something is commonly held or
frequently held
that's not a valid moral or epistemic
argument
and um i was personally aware of the
office thanks to lei
but didn't uh didn't read the last
edition of it until
recently and and it's interesting in the
context of our reading group because um
as i said so um it discusses at least
the
three chapters we'll discuss today are
applications of
probability theory to moral philosophy
something that is
highly important in the context of ai
ethics in particular
the second part we'll discuss is the
the application of probability theory in
in in the judgment
um made in a court
and the last part we'll discuss um
is what laplace called on illusions in
estimating probabilities or
in what 20th century psychologists would
call probably
cognitive biases maybe i can
even backtrack a little bit and explain
the context a bit of of this essay
so a bit of the history of the power of
poverty theory
essay so poverty theory was uh
like probably restarted uh around the
17th century with people like
with like karma or pascal um
and and then the more from bernoulli the
more
and so on uh but uh before laplace most
of the probability theories were
in a sense deductive uh meaning that we
had a
an inertial source of probability and
then we try to see the consequences
of this uh initial source of probability
uh so you start with axioms which are
the the axioms of probability
typically heads or tails would be one
half and half and then you compute the
consequences
of all of um and in 1776
uh pierre simon laplace uh like
so so there was this guy thomas bass who
did uh some work uh
in the meantime in england but it was
like he did not publish it uh it was
he did not really believe it in any case
like the
the most fundamental work an initial
work on
inductive probability theory was by
piercing lapis in 1776
uh and he basically put forward like
what we know
today as baseball as this uh rule to
go from the observations the data
uh so go to go from this to uh
general theories for instance uh due to
infer the laws of the universe from the
observations that we make
which which if my understanding is
correct
did that as an attempt to answer hume's
induction problem
uh so so base so it's not
well yeah so it's related to your
primary uh by
hume so david hume those fields of uh
beginning of the 18th century so like a
few decades before laplace
and base and hume asked this question
like if you see the the sun rise
every morning uh is it sufficient to say
that it will
rise every morning from
now on like is this generalization uh
uh like a a rule uh something that you
can uh
that you can uh yeah is it
a good way to think
and hume already had this intuition that
no it's not like exactly the right way
to think
instead we should think in terms of
probability the fact that we observe
the the sun rising every morning
increases
the probability that it will be rising
tomorrow
but hume did not take this follower like
he did not formalize
uh this idea he did not relate this to
the mathematics of probability theory
uh base did uh part of this work but
laplace this
did most of the work and uh especially
la plus
not only like solved with this this
kind of small primer i'd say but he
generalized this
and he he had this very uh very bold
claim and this
essay philosophic this philosophical
essay from 1814 the first edition and
then 1840 the second edition
uh is really like the the philosophical
approach to probability like like his
1776
essay was memoir was more like
mathematical
though it has a bit of philosophy of
course but it was more mathematical
and then laplace taught with this
probability course at the corporate
technique
in france after a while in
the late 18th century but
probably he felt that people were too
stuck too much to the mathematics and
did not really see the philosophical
uh uh importance of this work
and that's probably why he wrote this uh
this essay
and i think this essay is absolutely
fantastic i think this is
the i'm not going to make a lot of
friends by saying this but
i think this is the best philosophical
essay ever written
yeah and so this is say like well he
does
discuss a little bit of the mathematics
of probability but
the main point is that um there's this
thing he calls
a good judgment bonsang's in french
and he he kind of argues that this is
what
uh bright people are endowed with
in some sense maybe this is like one one
important uh one important precision
here about like
good judgments and muscles uh there is a
lot of misunderstanding around that
often translated in common sense
it's his it's not meaning common sense
in the term like intuition and the
commonly held beliefs actually laplace
is writing the last chapter where he
mentions
like slavery as a commonly held believe
that it's okay it's not okay
of course uh actually he's against
common sense
like good judgment not
um
people translates it to the bosons and
then bounce becomes
which is common sense and uh those are
radically opposed things like
it's clear it's really clear from from
especially from the french version
meaning good judgment and not common
sense
yeah and he's arguing against actually
common sense and commonly held beliefs
yeah yeah and his point is that you have
this
also common sense by held by most people
there's this good judgment held by uh
some some or some brighter people
and what he argues is that uh like when
you think longer you get closer to the
to the good judgment but what he argues
is that
good judgment is is still missing some
of the
important things for one thing it's not
very quantitative
and what he argues is that uh
probability theory
is the ultimate way of thinking
that there's this quote like he
frequently in this essay
discusses the fact that
good judgment kind of leads us towards
the right direction
but the computation of probability
theory the
calculated probability so probability
calculus will
is what gets us closer to it makes us
appreciate
what's uh the the exact and right way of
thinking
in essence so the essay is a lot about
this and it draws
a lot of applications of this very of
a very fundamental and general principle
like it's about how to think in general
so of course it's going to have a lot of
applications to
all sorts of fields and those we are
going to discuss
today uh are mostly uh related to
moral sciences and uh and uh
and lawsuits so to start by the this
first chapter
that we read from the book so why is uh
why our priority is important in a in
discussions about moral
moral philosophy so the the main
argument of laplace
is simply that the the world is
extremely complex
and even if we take a long time to think
and
have the highest ability to to provide
good judgment
uh people will make mistakes at
anticipating
the effect of return laws on the world
so uh if we see for example that there
are lots of crimes and we want to
to design a law to reduce the amount of
crime
it's a it can be done obviously but
it will sometimes have side effects that
are unpredictable
and and that's why laplace recommends
that
we should think of doing this kind of a
transformation of changes
but in terms of thinking about it in
terms of probabilities
so simply knowing that the effect of
that law
is uncertain and what we want is to be
able to
observe what this law is uh how this law
is affecting the world
and possibly change it if we see that
the transformation is not what we
expected
and this is this this will be this has
been very common that laws
are being changed over time as we see
that
they require improvement uh one thing he
discusses
in in this uh in this section is uh the
fact that
um it's often the case that we see
maybe part of the law that's never used
or that has bad consequences
uh in some points and you you may feel
like
we should remove this part of the law
and what laplace argues is that uh
it may be dangerous because we we not
predicting well enough the consequences
of of the law
and uh just so that we understand which
parts of the laws
are important and which are not we
should not rely
solely on on our judgment but also keep
track uh so there's this discussion like
it's almost an invitation to do uh
data science or to collect data or to
have a good database
to have a data-driven uh writing of the
law
uh and jose he he really encourages
people to to keep track of all of the
cases where the law was applied and for
which reasons
and to better understand what makes a
law good
i think this is uh not necessarily
specific to
you to property theory is more about
like the complexity of the world
uh i think there's a bit of a
computational complexity
theory behind it all and
uh and i i think it has a lot of
consequences to the way we think about
safe algorithms for instance algorithms
are supposed to make judgment as well
and maybe part of the algorithm is not
going to be used and you you may want to
just keep it because it's slow or
something like this
but the way you should be doing this
according to laplace is that
you should actually absolutely keep
track of a lot of data and to have a
data driven approach to
to designing uh what a good judgment is
but very well i just like to keep this
discussion accessible let's not just
mention algorithms because some people
think it's something complex just
decision making possible
like like especially if we're thinking
the the error of
us to think of decision making
procedures if you have a procedure to
make decisions
uh in a complex world where many data
are missing and many phenomenons are
interdependent in a complex way in an
intractable way you can't
track all the dependencies then then
this argument from laplace holds it
holds especially
in the context of decisions made by
machines and
like with lots of data that humans can
process but the argument is valid
in in in human judgments in in in in
courts
etc yeah later laplace
compares to two ways of taking decisions
the first one is uh using your intuition
and
the best you can do according to your
good judgment and the second one is uh
relying on collected data and writing
some privileges on paper
according to your common sense not your
good judgment
if you it's uh just keep them separate
according to your here you mean common
sense or your intuition
but it can also be uh the best you can
do to achieve good judgment and
the the second thing to uh to to compare
it with
is using collected data and writing some
computations of probabilities
on a piece of paper and coming up with a
result and it's a
it's usually a difficult effort to make
to
to accept that the the computation done
on the piece of paper is more trustful
than the 10 minutes you spend thinking
about uh
about an estimation in the general case
yeah it's a it's a really a general
theme of the of the essay
and it is well i guess it's a bit more
subtle than this because uh
uh laplace acknowledges the fact that
most of
the time you can't reduce things through
computations it's a very frequent
uh uh concept in in the in in the essay
that he often
says that we should try to reduce things
to computation
but sometimes uh things are too
complicated to be a
smart organ to be to be submitted to the
computations it's like
this computation is like an overall it's
like a
computer you can imagine today and if
you can
formalize everything like the problem to
it
then it it will give you an answer but
more often than not
like the problem is too complex for you
to write it down and to ask the computer
what do you think and then uh
laplace argues that in this sort of
situation you could then think in terms
of
of analogy but you should be careful
about to each
extent that the analogy holds
but the analogy that uh that laplace we
currently uh
discusses is uh what like having this
uh this box with balls inside of it and
you don't know what all the balls inside
of it
and so
he uses the the the the was the thought
experiment of drawing a ball and
for instance observing that you drew a
black ball then the question of
laplace's what is the probability that
all of the balls inside are black or
whatever
the next ball that you draw is black and
he's using
this very uh this thought experiment
that's very remote from
from from the low of from everything
but somehow he sees like he constantly
in the essay found connections between
this very thought simple thought
experiment and actual
problems that you face from something in
the court of law
so one example he he gives uh
in the essay is the example of a
testimony
so this is clearly very important uh
in the law to have testimonies
but there's always the problem of how
much you do trust the person who
who gives a testimony and so
well
laplace has all this very really nice
discussion
but essentially what he says is that um
they are like uh if some some event is
extremely unlikely uh a period like you
you like for instance like uh
so a murderer is like very unlikely a
period like most people
don't murder another person uh
then um if somebody tells you that
that there was a murder what you should
compare is the probability
a period of this model with the
probability
that uh the person who who
who gives the testimony is uh either
lying or
being mistaken now this probability of a
person lying or being mistaken can be
small
but probably like it has to be very very
very small to be comparable to the
probability of a murder
and so this is the kind of probabilistic
thinking that uh
that this essay is talking a lot about
uh and it really answers also like some
of the questions that that
david hume raised earlier in the century
yeah a famous quote mentioned about this
topic is that
extraordinary claims require
extraordinary evidence
yeah and this is something you can read
if you if you look closely at a base
rule
whether how much the probability you are
assigned to some theories
and some unknown theory will change is
dependent on the probability
of the observation and if you make
extremely unlikely observations
it will change more the how much you
your beliefs in different theories
yeah yeah
another very interesting aspect of
probability theory applied to the to the
context of the law is
uh the fact that when we rise the law
like most laws are written
as uh if the person is guilty then
uh do something and if the person is not
guilty then do not
do something else and this kind of of
of principle of rule this kind of
algorithm
uh requires perfect knowledge of
the whether the person is guilty or not
and yet in practice uh we
we have to expect that we're only going
to have limited data we're not going to
be able to have a mathematical proof
of the fact that person the person is
guilty or not we only have evidence
we only have data that will uh
change what we believe that will update
our probabilities
but there may and quite often there is
still a huge amount of uncertainty
when the sentence has to be given and so
what
laplace argues is that the the law
we should think more of the law as or we
should write more the loop or maybe not
right because this is difficult but we
should think
at least of the law as more something
like if the person has a
high probability a party larger than 99
of or 90 let's say of being guilty
then we should give him this sentence
and maybe we can
then have a different level of sentences
depending on this probability if the
priority is between 50 and 90
we have also half half ruling but not
as half as it is as if it were larger
than 90
another another illustration was just
like the introductory paragraph of the
the application of poverty is to to to
to to to the law
and the and and the the court ruling
the the the the fact that we have this
uh first install like the first tribunal
and then you have the appeal
and then appeal you go to a tribunal and
like
argues that in the appeal you need more
judges
and you need a majority vote etc because
like the probability that
an error was made in the first uh so
just like the
this in terms of probability thinking uh
this would just boil down to to the
wisdom of the crowd like wisdom of the
crowd but not
every crowd the crowd of churches yeah
then
he's making a probabilistic argument for
the fact that if you go to appeal
you need to increase the level the the
number of judges
uh before you you you finish the
procedure
yeah and there's also to go back to the
threshold that uh
that leo was discussing about the fact
that we can't be absolutely certain that
someone is guilty but we should uh still
send that person to jail if there is a
high priority that that person is going
to do
this sounds quite powerful because it
means that with some frequency
we are going to to put some innocent
people in jail
and some some something else that is not
desirable
is that we release free some uh some
some murderers that would kill other
people
so there's this balance between a civil
and desirable outcome
and because the system is not perfect
then we can't have a perfect knowledge
so these algorithms should we should not
even try to rely on perfect
perfect knowledge then we we have to
to accept that the the system is going
to make mistakes
we can think of it as a we can do our
best to improve it but
there will be some mistakes and choosing
this this probability of
how should we need to be to send someone
in jail it would be a balance between
the undisabled effects of uh of putting
innocent people to jail and the
undisabled effect of reducing a
murderer free again just i'm just adding
adding
just nuance here uh so laplace is not
saying that
like in all cases it would be
impossible to have close to perfect
knowledge just arguing that
in many cases knowledge is hard so we
have to have
so then we go to appeal etc but then he
says like
in easy cases where it is easy to
establish
close to certain like like
everyone in the village so this person
murdered this person
and then like when the judge saw the
killer kill the victim
then you don't need to go to appeal you
don't need to do this sophisticated
probabilistic thing
just like just to to close the door
because sometimes when we we bring
in relativism like this one that's like
we can't always know perfectly etc
some people interpret it in the wrong
way and say okay then everything is
relative we can never know
no no like laplace is not closing the
door
to the easy creases there are easy cases
and in these easy cases
the simple almost binary way of thinking
is practical
and is enough so we're not ruling out uh
simple and close to binary thinking it's
just that in complex
cases where it is clear that no one has
complex like
everyone has only partial knowledge for
example
evidence has been destroyed for example
like the the evidence was destroyed
either by the the guilty person or the
likely guilty person or by someone
who would like someone who is really
guilty and would like to
to make the accused person look guilty
so for example those cases those are
complex cases where we need this
relativistic thinking probabilistic
thinking go to appeal include the number
of judges
laplace is not ruling out uh so
so raplace is not a relative is
relativist for the sake of being
relativist
and sometimes i read uh in some part of
the literature
like people using laplace uh reasoning
to say that okay knowledge of
truth is always relative and it's like
and then they rule out
close to certainty cases like there are
cases close to sensitivity is useful
i agree that is a common mistake and uh
it is good to
to mention it sometimes it's uh this
mistake is described with the
with the image that uh people think in
black and white so
absolute certainty of false absolute
certainty of true and
this is this is the wrong way to to to
to think obviously
but then when when they realize that oh
nothing is
either black or white things are gray
they make the mistake of having only one
shade of grey
and uh and thinking in terms of
varieties you should
make your priorities go from as close to
zero as possible to as close to one as
possible obviously in
many cases but also have priorities in
the middle
in for difficult cases that are
uncertain and so
you should think of all you should think
with all the shades of gray from a
white as close to one as possible and as
close to black
zero as possible very dark grey for
things that are extremely likely to be
false
yeah there is some very nice quote in
the essay
which early on in the essay where he
discusses uh
the fact that what is probability theory
or we can have another episode on this
but
what is the probability but uh
essentially what he says is that a
probability
is a description of our ignorance
and of knowledge
where we will discuss the introductory
part of the book so
it's country intuitive now we're
discussing the the final part of the
book
of the book so moral philosophy or law
etc
that we will go back and discuss the
introductory part of the book
why probability theory matters yeah
i just like to put this to close this
part on relativism so just like to make
it short
um we like there's a lot of literature
on the confrontation between binary
thinking
and derivativism and actually priority
probabilistic thinking
uses both like there are cases where
it's useful to be a relativist and to
have nuances and to
to defer your judgment and delay it like
to delay it as as as long as possible
and there are cases where it's very
useful and practical and
and fair to have close to binary
thinking so
you should not through binary thinking
when it's useful
and you should be aware that you you
should be like
you should not use it always and you
should be aware that complex cases
uh are do not like are not solved
by binary thinking yeah
yeah and so just you to close the the
section
on uh on the law uh
there's also a nice discussion about um
so so
let's say what we care about is actually
uh this probability of the person being
guilty
and we want to make sure that it's
larger than some high threshold
so that we can convict the the suspect
uh and and then la paz has this
discussion about
if you grow the size of the assembly of
the number of judges to
to to give the the ruling um
like should you demand that a larger
fraction
of these or a smaller fraction of these
well what is the fraction of these that
need to to
to say that that the person is guilty so
that we conclude that the person is
indeed guilty
and uh well this next question like if
you have a very
first hole that's very close to one half
uh
then um uh then
if you have a small number of judges
then it's very very bad
uh but essentially what but uh the
conclusion that laplace uh comes through
is that uh with a rough estimate
uh is that uh out of an assembly of 12
people maybe there should be something
like nine judges
that say that the person is guilty in
order to convict the the
the individual and i think it's it's a
nice
way of having the prime like you demand
more than the majority
not because not because
well that's a an arbitrary rule but
because you want to have a high
probability
to we want to conduct a person only if
there's a high probability that the
person is guilty
i think it's a it's a nice way of
thinking about this problem
yeah and it's just uh
the fact of accepting that mistake can
be made that the jury will not be
perfect if the jury is perfect
either 12 will always agree or okay 12
the 12 will always agree because they
are perfect this is not the case so
in the model that laplace
discusses the in the model that let us
discuss is uh
the jury are considered to be quite good
better than chance at deciding if
someone is guilty or not
maybe they they get it right with the
priority of 75 percent
something like this and this is how
laplace run these computations yeah
now one caveat to laplace's computation
is that
laplace assumes in his model that
the the the members of the of the
of the jury are independent like the
opinions they have are independent
and unfortunately we know by now that
there's a lot of of correlation of group
polarization effects when you have an
assembly
uh so this is a caveat to be given
to this analysis of laplace which would
demand
maybe uh even larger but yeah
it's it's a complicated problem
because they are shown the same data
it's uh surprising to expect that they
would be
didn't make independent judgments so one
of the last sections of the essay
this is called on the illusions and
estimation probabilities
and uh it's also absolutely fantastic
like it's
uh like 200 years ahead of its time
[Music]
essentially uh well he
he he discusses the way people think
poorly i guess that
that other philosophers have noticed
that people were not always thinking
very very clearly
but what's really nice is that now that
he has this uh
post rate that probability theories
positive is the right way of thinking
then you can measure how people deviate
from this
right way of thinking and uh in doing so
like he discusses essentially all the
the best known uh cognitive biases that
we we know of today
uh like for instance uh the badass
policy is like
if you only see a stream of like no no
if you see
a lot of of of uh
red uh coming up uh in the
roulette in in casino uh lately then you
might be tempted to say well the next
one is not going to be red because it's
come too often something like this
but lapis argues that this is a
an illusion and then he discusses things
that are
probably closer to what we would known
as call today cognitive
bias like familiarity bias motivated
reasoning i think
these are the two main that he he really
stresses
uh in this essay and
he does this in a very very compelling
way so uh
i think this is really really really
fascinating section
yeah one point that i that i that i'd
like to write is that uh
usually people underestimate how much of
what they observe in the world
happens simply due to randomness so with
the example of the
of the lottery
a lot of people try to find out
explanations of
why this this number came out and one of
the explanation is that
some numbers come the number 47
didn't come for for two years and it
it's bound to happen at some point so we
bet on this one
other sort of explanation is that there
are people that would
log all the numbers that come out of the
lottery and find the numbers that come
the most often
and then try to bet on these numbers
because they have been observed to come
more often
but but uh and laplace discusses that he
simply
created a small model of uh of
generating uh lottery numbers
and finds out that yes we expect that
in if you if you observe past data there
will be some numbers that came out more
than others
it's a normal thing simply due to the
random process
and because you find such a simple
explanation
you need uniformly random randomly
generated numbers
to to explain what i've been observing
one should not think that there is a
different
processes for generating these numbers
than the simple process that laplace
that that that laplace described and
that is actually the lottery
yeah and it's related to this idea of
what poker players call the resulting
buyers
uh so that's like judging uh the
decision of someone like uh
like whether he was right to play number
five in the lottery
based on the result and you say oh i was
stupid i did not play fight
the number five for instance uh and a
poker player would
say that uh this is a very very very
very bad habit
at least in poker because you you
give too much attention to things that
are just noise
and you're going to update your strategy
based on this and you
you're not going to to focus enough on
your decision making because this is
what matters this year making
so typically in poker players
professional poker players
uh there are these groups of poker
players who who just
never discuss like the so-called bad
beats the way they
they lost in a tournament like the
specific hand the larson
even though it was highly unlucky
because what they care about is like the
decision making
what it is that you choose to do
when you had this uncertainty and based
on this uncertainty
what whether what you did was good or
not and not based on the result
you should judge based on the
uncertainty and not based on the result
i think this was one of the this is one
of the the greatest insights of
probability theory
yeah and this is very hard to do in
practice i often reward rewind myself
for making decisions that
ended up doing good and to punish myself
for making decisions that ended up being
bad
and and i learned because of the result
and today it's hard to
to do differently yeah
think about so to to illustrate this
with
the example of lottery lottery is well
known to be a game with a negative
utility
negative expectation of gains
so if you judge a decision process that
either decides to take the lottery or
not
it is very easy to to to agree right now
that
the the decision process that decide to
play
is making wrong decisions when the
decision process to decide not to play
is making correct decisions
but now if you if you imagine you see
someone that decided to play
and won then it it is very unintuitive
to say that the
the decision to play for for that person
who won
was a wrong decision a decision pushed
by a
decision process that does not correctly
maximize its expected utility
simply because of the results and this
can lead to too difficult discussion if
you
discuss with someone they might tell you
you don't know where they are making a
good or not decisions because we haven't
seen the result yet
yeah yeah that's not politics
like let's talk about like uh
confirmation bias
yeah the confirmation bias and the
example of liveness
so uh there are like i don't know if
like the audience is familiar with like
some uh beliefs like a numerology like
people who believe in like the power of
numbers if this number
pops out and then there's i don't know
if the
the the golden ratio uh in something
then there is something special about
this object
and um this is something still common in
today
people like uh like
believe in in miracles just because some
sequence of numbers appeared i don't
know in the date of birth of some singer
and then the date of release of her
album
or or his album and then they will start
like building up theories and the
internet is very good in amplifying
these theories that
because the the date of birth of the
singer and her date of release of the
album and then i don't know
9 11 appear like happened and then you
the radio between two so so this is this
is something that
sounds funny but even great minds
uh were not immune to it
and he he gives the example of leibniz
and um
and and bernoulli also uh and that's
also not like mostly libraries like the
bernoullian libraries computer this
series like it's a theory of
number that gives some special results
etc
uh done by bermudian lightnings but
leibniz used this result
to argue with the chinese emperor that
god exists
[Music]
god might exist for other reasons but
not because the series
is equal to one over two or so he's like
he he he he
so leibniz who was a strong believer uh
knew that the chinese emperor loves
mathematics
so he thought like yeah maybe like this
would convince him of
like christian god and christianity and
then he sent him
like a funny note on the results of his
series and say look
if you sum these numbers and then you
obtain one over two or one or one over
four like one over two right
one over yeah i think it was one over
two yeah one over
one over two and then look this this
like you create something out of nothing
and this is this is how god operates and
this is a proof
and laplace argues that like this like
laplace does not call it confirmation
bias
but today in light of what we know since
the 20th century all the work on
cognitive biases this is the clear
instance of cognitive bias
you believe something is is true so you
believe god exists you believe in
christianity or
islam or judaism or whatever so and then
you have a strong
bias towards confirming like validating
everything that comes from your religion
or
your ideology communism or capitalism or
whatever you want
and then he goes on with examples like
that and so
i believe this this chapter on the
illusions of computing probabilities if
you want to rename it today
in light of the developments we had in
psychology it can be called
uncognitive biases actually like you can
you can argue that
what he calls illusions in computing
probabilities
are cognitive biases actually so that's
so so i mentioned this uh
so the confirmation bias and the case of
leibniz
who practice like who's almost falling
to numerology to argue for a christian
god
but then there is the
uh i don't know a hybrid between
confirmation bias and
familiarity bias maybe more like
familiarity bias in
modern terms which is this this the
thing that
it's not because slavery is commonly
accepted that it is okay
so and it's it's not like it's not
because
in some culture some practice is
commonly
accepted then this practice is morally
good so
so maybe we can even argue from this
chapter that
as as people who who learn political
theory
we have a moral duty to go beyond
the commonly held moral standards of our
culture
of our time of our era of our
i don't know region or and then for
example like
you mentioned slavery but we can go on
make a make a case for
like just moral progress for example
like moral progress is debated in like
moral progress
versus uh moral relativism so
uh not sure if i'm exact but
uh like in moral relativism people would
tend to tell you like
you have to respect the moral standards
of some
culture or some region etc uh
for example let's say like there is a
region where people
don't let girls to school for example
like should you respect
should you respect this practice because
it is a it is the commonly held
moral standard of that region or or
should you
like should you try to go beyond that
and and the
the if you read the the the chapter of
labs
you can't come up i personally came up
with the conclusion that
when you when you learn probability
theory you have to
work with it and think with it and think
harder and try to always go beyond
the commonly held moral standards of
your time and of your
of your group your social group whatever
that social group
yeah uh yeah so the the connection with
probability theory may be uh a bit loose
in the
the essay itself i think it's more like
a point that uh
well these are quality biases that
people have but
um and i don't think laplace knew about
this but but there are actually a strong
connection with povt theory
so on the confirmation bias for instance
uh
parliament there's actually a theorem in
uh
invasionism that says that
the expectation of the posterior is
equal to the fire
so you should before looking at the data
you should expect to have in average the
same opinion after looking at the data
then prior to looking at the data
and intuitively the reason for this is
that um
uh like the data can make you go both
ways
uh like if you're surprised that the
data
is suggesting something like like say
like you you sign a probability one half
of
trump being re-elected i don't know
something like this
then and then you you you expect that
tomorrow you're going to have the same
opinion
tomorrow at the end of the day it's
going to be positive one half as well
but this may evolve it's not going to be
uh exactly one half for sure
even though you see a tumor if tomorrow
you see data
that suggests actually the popular of
the popularity of trump is is
decreasing more than you expected
then you should decrease your
probability but if you're surprised
that it's maybe it's decreasing but not
as much as you expected
then you should increase your
probability uh
about the reaction of trump uh so
whatever happens in average you should
have the same so that's
actually a theorem just just to make the
connection with poverty theory uh even
less loose
so for example uh uh the what louis said
like
many things are just due to just to
randomness and
and like that you don't need
sophisticated theory to explain them
uh you can you can see that as some form
of
okan's razor so you don't need
sophisticated explanations
like it's not because um uh it's not
because uh
the the moon is like that and the number
of girls who were born that month and
the number of
boys who were born that month and the
date of birth of of your husband or your
wife is like that
that you would have a girl or a boy you
would have a girl or a boy just out of
probably randomness genetic rankles and
how many how many y chromosomes
the the the husband produces and and etc
and it has nothing to do with the moon
and the numerology and sophisticated
computation of astrology etc
uh and like his book makes a very good
case for all comes razor with
probabilistic thinking so laplace in in
laplace
in napla's writing the connection is not
straightforward
but we can argue that um many of the
illusions he talks about laplace talks
about
are some of them are due to uh a bad
application of occam's razor so occam's
razor is displayed principle in
epistemology that tells you that
out of many explanations you should
always favor the simplest one the
the shortest one the one that does not
require a lot of
additional assumptions and like in the
case of the illusions
uh laplace is mentioning a lot of these
illusions involve additional assumptions
that the moon and astrology or whatever
neurology and the number of girls and
boys that were born that front and i
don't know the
existence of christian god so those are
like unnecessary
assumptions and is very well known for
actually uh
he uh his way of practicing occam's
razor so
in his book on mechanic celeste right
yeah i can't remember the title but yeah
mechanic like
it's like the sexual body emotions of
the body
the whole emotion of celestial bodies
there was this famous
famous argument he had with napoleon
napoleon would tell him
i don't see any mention of god in your
book
and then laplace just replies or is
believed to have replied
sir i just didn't need this assumption
so this is an instance of falcam's laser
and
we in this group argue that organs razor
is just another way of being the union
what's uh component it's not sufficient
but yeah they still there it is
something important to note concerning
uh confirmation biases
so even though you you you might have a
correct prior
and uh apply a camera raiser quite well
confirmation bias is something that
happens at the moment where you
you look at evidence and the problem is
that
sometimes people would look at evidence
and no matter what is the evidence
they would change their belief in the
same direction yeah which is a what
cannot happen because as they said
that have when you look at the evidence
in average
depending on what the evidence is you
you your change of belief should should
serve up to zero in average
so that means that if the evidence
points one way you should change a
beautiful way and if it pulls the other
way you should change it in the other
way
a famous illustrative example for this
was the
the condemnation of of dreyfus who was
accused of of something and when people
look for proofs
about this they could find no they could
find no proof
and uh unfortunately uh finding no proof
they concluded that oh yes he was guilty
and
good at hiding that his gucci so i
accidentally
that's an excellent example let's let's
elaborate on this example maybe to
conclude so just
to put more context uh to the
english-speaking audience
alfred dreyfus was a captain in the
french army
and uh they were grouped and the
atmosphere
was was was uh was so back then
in france was uh quite anti-semitic
so in an anti-semitic context alfred
dreyfus was
uh accused of intelligence of being a
spy
a german spire on english by a german
spawn
guessing germany uh jerusalem and the
evidence
against him was a note uh
that was presented as a notes dreyfus
right
to the germans and and then ponca
so holy point polymath one of them
last 40 months as people say used
probabilistic arguments
to to to to to prove the innocence
or to arch for the innocence of
religious
if you found no proof and then you
change your belief
to to increasing how much you think that
that person is guilty
if you if you are if you correctly apply
base law it means that
if you had found proof you should have
updated your belief in a direction that
is not guilty
so when you observe a like you you make
an observation
and you update you believe one way it
means that if you had made the opposite
observation you should update your
beliefs
in the opposite direction and obviously
finding proof of someone guilty
should increase your beliefs in the
direction that this person is guilty
and it means that not finding proof
should always make you update your
belief in the direction that that person
is not guilty because
or at least slightly otherwise otherwise
you
you are in in the in the failure of a
confirmation liars
yeah yeah that's like uh
like this was that this is uh easy to
say
in theory in practice it's always harder
when you actually presented the evidence
and you're always trying to find
loopholes and an explanation for why you
go in your direction
so one way to to better combat this
tendency that we all have to motivated
reasoning
is to pre-commit um so so ideally you
just apply baseball you just apply
the laws of quality but uh be because we
have limited uh
we have motivated reasoning one way to
to combat it is to pre-commit me
meaning that you're going to say well
today i believe this
i believe that refuse has a 70 percent
idea of being here
i've been guilty and i know that
they are going to look into this uh this
piece of evidence
and i'm going to do to predict what it
is and i'm going to say
well i think that uh it's going to be
something like that
uh and if it's uh so let's say that for
instance
uh it's the number of uh of messages he
sent to some
general in the in germany
and you say well probably he sent like
five messages
and you're going to say well that's my
prediction and it means that
if there are more messages than this
then you're going to increase your
poverty that is guilty but if you there
are less
messages than this then you're going to
decrease it and you have to
well one good way to do is to pre-commit
and so
uh this is more generally a good habit
of a beijing which is to to
bet visionism and betting have
strong connections uh historically uh
and still today
and betting is good because it forces
you to
explicit your prayer and to pre-commit
and and to to verify that you're not
going to do
uh motivated reasoning and so
yeah i think this is a one of the
important takeaway
of probabilistic thinking yeah yeah i
really
totally agree with that uh advice from
lake uh another
advice i could be that is slightly less
good but uh
maybe easier to do in practice also is
to simply when you
when you see yourself in the process of
updating your bills based on evidence
so if you are already doing this i think
it might be useful to
to ask yourself the question how should
i update my belief if i had observed the
opposite evidence in that case you it
might help to detect
when you are actually lying to yourself
and doing confirmation bias
and help you choose in which direction
actually the evidence points to
so next week we will discuss a very
important paper gender shades
by joy biolumi uh and uh and the timnit
uh that paper was important in in
in showing empirical evidence that
facial recognition is biased
uh and it has strong biases that make it
not ready to deploy
and thanks to that paper and the
research follow-ups by these two
researchers and a few others
now there is a moratorium on not
deploying facial recognition by many
companies so
ibm then microsoft and many others
followed
stated they would not deploy facebook
recognition and they will not use this
especially for police and military use
so we'll discuss that paper the some of
the follow-ups and and what what does
this mean for today's
technologies such as so we'll focus on
facial recognition but we'll probably
discuss other aspects of biases that
need more restoration and more work
uh by by people who work on artificial
intelligence and computer science
and moral philosophy of course well
thank you and see you next week
bye