We received a wonderful example of -- for the kinds of bargains we studied
in the weeks on inductive reasoning.
We studied generalization, and we studied applications of those generalizations.
And using that for causal reasoning that we tested by manipulations
and by the sufficient condition tests,
and all of those are brought together in a wonderful little video.
So, take a look.
>> Hello.
My name's Catriona, and I live in Sweden.
I've spent many years, eating a little bit of chocolate everyday.
And I've always strongly believed that eating chocolate makes you happier.
In other words, most people will be in a better mood
after they've eaten chocolate than before.
And I'll give you four pieces of evidence
in support of my conclusion.
Evidence one: I've met a lot of people over the years
and when I give them some of my chocolate, they always seem happy about it.
I can't think of a single case of someone eating chocolate
who hasn't looked satisfied afterwards.
Evidence two: It could be that
eating chocolate isn't really causing their happiness.
They're just happy people eating chocolate.
So, I asked unhappy people whether they ever eat chocolate.
And they confirmed that they do, precisely because it cheers them up.
Evidence three:
Now, I went to a chocolate factory where the workers get free chocolate every day.
And these people could theoretically be unhappy like the rest of us could.
but they all had smiles on their faces, and some smears of chocolate.
Evidence four: You may ask whether these people are also in love
and it's love that's causing the happiness,
not actually the chocolate.
So I had to find people who eat chocolate, but are not in love.
I did a mini survey at my corner shop.
And 80% of the people who responded that they were not in love,
reported that they definitely felt their mood improve
when they ate chocolate.
So, it does seem to be the case that
eating chocolate is probably sufficient to improve your mood.
Obviously there are people who never eat chocolate and are very happy.
For example a successful dieter or your dentist.
You can find happiness by falling in love or getting promoted
or finally reaching the top of Mt. Everest, whatever's your biggest dream.
But for an instant helping of happiness,
chocolate will cheer you up, mm.
>> Wasn't that great?
I already knew that I loved chocolate
and that it improved my mood,
so maybe I was convinced by this argument
because, I already believed the conclusion.
And that's when you ought to be careful.
When you look at an argument, and it's for a conclusion you already believed,
then there's going to be a tendency to think it's a great argument.
so if you really want to know
whether it is or is not a good argument.
You gotta look carefully at the ones that are trying convince you
of things that already had a tendency to believe in the first place.
So let's look carefully at her conclusion.
Catriona's conclusion was very carefully qualified.
On the one hand, she said that chocolate is one of the things that makes you happy.
She doesn't claim that it's the only thing
that makes you happy: you know,
Love might make you happy, climbing Mount Everest might make you happy,
all kinds of things can make you happy.
She's only claiming that chocolate's one of them.
Another qualification, is that she says
chocolate will probably improve your mood.
She don't say it's definitely,
don't say it works always, or for all people.
But it'll probably improve your mood: so it's an inductive argument,
and she doesn't have to prove it beyond a shadow of a doubt.
That's a good move in an argument, because it's very hard to prove things
beyond a shadow of a doubt.
But there is one part of her conclusion that makes the argument difficult.
And that's that she says chocolate improves your mood.
Now that's a causal claim.
That's not just that you eat chocolate and you also happen to be happy.
That's that eating chocolate causes you
to be happier than you were before,
that is, to be in a better mood than you were before.
So let's see if the different bits of evidence that she presents
really do support that conclusion.
So the first bit of evidence that Catriona provides is this.
"Now I've met a lot of people, over the years, and whenever
I give them some of my chocolate they're clearly happy about it."
What kind of argument is that?
That is a statistical generalization from a sample,
because she hadn't met everybody in the world,
she's only met some people.
But the sample that she's been able to check, they've all liked chocolate.
She adds one more claim:
"I can't think of a single case of someone eating chocolate
and not looking satisfied afterwards."
You know, this is kind of repetitious,
because she says she can't think of a case.
She just told you that whenever she gives them chocolate, then they're happy
and if they're happy they're satisfied, and so maybe that doesn't add too much.
It's still a generalization.
What are we going to think about this generalization?
Well, let's assume that she's got a lot of friends.
So, she's checked a lot of people, she's given a lot of people chocolate
and -- and they're all happy.
Well, is the premise true?
Well, do we believe that every single person
that she gave chocolate to was satisfied and happy?
I kind of tend to doubt that, Catriona, sorry, but --
it's just, such uniformity is unusual among human beings.
And so my bet is that a couple of them didn't.
But notice that she didn't really need that, because
she's only arguing that giving chocolate will probably improve your mood,
not that it always will for everybody.
So she doesn't need that strong claim about everybody.
So she's still on pretty firm ground with regard to claiming that almost everybody,
or most of the people, have improved their mood when she gave them chocolate.
We still might worry about a bias sample.
There might be some cultures out there, or some types of people out there,
that don't like chocolate.
Maybe they're allergic to chocolate,
or something like that, that would be really sad,
I'm sorry to even think about that, it makes me sad.
But, there probably are, and they're people that don't like chocolate.
And so, it's not going to work for them.
So maybe she wants to qualify her conclusion a little bit, you know,
"among the groups that I've met:
different cultures might be different,
different biological conditions might make people allergic to chocolate."
But, with regard to most of the people she's met,
chocolate seems to work pretty well.
So we've got now a statistical generalization:
"Most people, if you give them chocolate, it improves their mood."
Great.
What does that show you about you, because remember her conclusion is
that if you have chocolate, then that chocolate will probably improve your mood.
So now she needs to take that generalization
and apply it back down to you as an individual,
to make a prediction about what'll happen to you if you eat some chocolate.
So in this particular bit of evidence, she needs to generalize up
to "most people will have their mood improved
if they eat chocolate," and then back down again.
And since that's true with most people,
and you're not special in any particular way
-- or it would be a conflicting reference class fallacy --
since you're not special in any particular way,
the chocolate will also improve your mood.
That's the way this first bit of evidence seems to go.
So now we're ready for her second bit of evidence.
Let's get all adjusted here
so that we can think about this new bit of evidence that Catriona provides.
Okay, what she says is:
it could be that chocolate isn't really causing the happiness.
Maybe they were just happy before eating the chocolate.
Now, that's a problem.
If you're going to say that it improves people's moods
when they eat chocolate,
it's not good enough that people are already happy,
and then that makes' em want to eat chocolate.
And so they eat chocolate to celebrate how happy they are.
Well you gotta prove that it actually does cause the improvement in the mood.
Okay, how are you going to do that?
Well, we looked, in the lectures on induction, at causal reasoning.
What you need to do is manipulate.
You want to look at people who are not happy
and see if the chocolate makes them go up in mood
and manipulate the amount of chocolate, manipulate how happy they are,
and see how those have effects on each other.
And that's how you decide among the hypotheses.
And that's exactly what
Catriona does.
"So I asked some unhappy people whether they ever eat chocolate,
and they confirmed that they do, precisely because it cheers them up."
Ah, so now we have a sample of people, where we've manipulated their happiness.
We've looked at happy people and unhappy people.
We've looked at people at times when they're happy
and times when they're unhappy.
And then we can look at their chocolate consumption
and we can check to make sure that they're happier afterwards.
It's just like checking whether smoking causes cancer.
We talked about that in the lectures on induction.
If you want to know whether smoking causes cancer,
what you do is you induce smoking in creatures
-- in this case, lab monkeys -- that did not previously smoke
and see whether that increases their cancer rate.
And what she's doing is she's saying:
"let's take people that don't have happiness,
give them chocolate, and see if that increases their happiness."
So she's using exactly the kind of manipulation test
that we talked about in the lectures on induction.
Good job, Catriona.
Now let's switch to the fourth bit of evidence,
and I want to get ready for that one too.
Now, what Catriona says for her fourth bit of evidence is:
"you may ask, what if all these people are also in love,
and it's love that's making them happy, not really chocolate?"
Because remember, she doesn't want to claim
chocolate's the only thing that makes you happy.
Love might be sufficient for happiness,
just like chocolate also causes happiness.
How are we going to tell which one it is?
Well, in the lectures on causal reasoning,
when we were looking at the tables, and the diners who died
from the poisoned food, one of the points that we made
was that if you have two candidates for a sufficient condition,
you've gotta look at situations where one of them is present
without the other and the other present without the first one.
And that's exactly what Catriona does.
She says, I had to find people who eat chocolate, but are not in love.
Whoa, well that's what you're looking for,
because if you have some people who eat chocolate,
but are not in love,
and some people who are not in love but eat chocolate, you can test it.
And what did she find?
Well: "I did a mini-survey outside my nearest corner shop,
and 80% if the people who confessed
that they were not in love
said they definitely felt their mood improve when they ate chocolate.
Notice she's not claiming it's so universal, 100% anymore,
she's down to 80%: good move.
But in addition, she's now ruled out that it's really the love
that's the only sufficient condition: even when the love's not present,
you still get happiness with eating chocolate.
So that's applying one of the tests that we talked about
in the section on causal reasoning to test for sufficient conditions.
Okay, we've done our bits of evidence one and two and four.
We skipped over number three.
So what's your third bit of evidence? Now, we've gotta look at that one.
Okay, what Catriona says is: "I went to a chocolate factory
where all the workers eat chocolate every day."
Not only that, it's free.
Free chocolate! Yeah, mm!
I love it.
"Like everyone else, these people could theoretically be unhappy,
but they have smiles on their faces."
Wouldn't you?
Free chocolate all day long.
But wait a minute, wait a minute: is this a good argument?
Like I said, it's a conclusion I like.
But we still gotta look at it critically.
Sorry, Catriona, these people are happy,
but how do you know that they're happy because of the chocolate, right?
They've got a job in the factory, It's good having a job.
Chocolate's very popular, so maybe the factory's doing really well,
which means they can pay them more money, better benefits, good job:
maybe that's what's making them happy?
Sure, all these people in the factory are happy.
But it might not be the chocolate.
It might be the fact that they got a good job.
So I think this fourth bit of evidence is not really all that strong.
Her number three, by the way: the fourth one we considered.
It's not all that strong: now, what does that show you?
You could say: "Wait a minute, she's got four arguments,
one of them's no good, so it all is back to nothing.
But of course, that's not the right way to think about it.
She gave us four bits of evidence.
If one of them doesn't work, and we've only got three left,
we've still got three left.
So if those first three bits of evidence are good, and if they show at least
that it'll probably improve your mood, and they establish
the cause of conclusion that she claimed, then it seems to me
she's given us pretty good evidence for the conclusion she was claiming.
And in doing so, she's exemplified a lot of the different forms of reasoning
that we studied in the weeks on inductive reasoning.
So, thank you very much, Catriona,
for submitting this wonderful video, this wonderful argument.
We all learned from it and we appreciate it.