(intro music)
Hi, my name is Caspar Hare.
I'm a professor at MIT,
the Massachusetts Institute of Technology.
Today we're going to talk about science.
Can it teach us everything[br]there is to know about reality?
Science is an impressive thing.
Scientists have, for hundreds[br]of years, been able to predict
the movements of comets,[br]the eclipses, and the like,
decades in advance.
In the 20th century, scientists were able[br]to
transplant hearts,
to send people to the moon,
and do all kinds of extraordinary things,
of which we can hardly even imagine
what they'll be able to[br]achieve in the 21st century.
There's an issue though.
Just how impressive,[br]or how good, is science
at describing the world that we live in?
One strong claim that[br]we might make is that
science can give a complete[br]description of reality.
It can describe everything that there is
to know or be known about the world.
Now, at various points in history,
people have disputed this.
They've thought however[br]impressive science was,
there would be no way that it could give
a complete description of reality.
There would be things like[br]angels, spirits, and the like
that could not be described[br]in the language of science.
Today, what we'll do is we'll[br]look at a modern argument
to this effect.
To the effect that are aspects of reality
that cannot be described[br]in the language of science.
Our first job is to explain what it is
for a description of an aspect of reality
to be complete.
We'll do this by way of an example.
Here's a description of what's going on[br]in a room (it happens to be this room):
there are three people in the room.
End of description.
Was that a good description?
Well, you might think that there are[br]things that the description left out.
I said there were three[br]people in the room.
I didn't say anything more about them.
I didn't say whether they were[br]standing up, sitting down,
whether they were riding on[br]little horses around the room.
There were bits that my[br]description left out.
I could have told you more.
I could have said, "There[br]were three people in the room,
sitting around a table."
End of description.
Still, my description[br]would have been incomplete.
I didn't tell you their names.
Maybe they were called Ben,
Balthazar, Fitzgerald.
Maybe they were called, as[br]they actually are called,
Damien, Gaurav, and Caspar.
Let me add that to the description.
That their names are Damien, Gaurav and[br]Caspar.
They're sitting around[br]a table, in this room.
Still, there's lots that I've left out.
I haven't told you what they're wearing,
I haven't told you anything[br]about their heights,
about their ages, about[br]all kinds of things
concerning these people.
These are all details[br]that I could fill in.
Suppose I went on,
and I added layer upon layer[br]of detail to the description,
I said more and more about[br]the people in this room,
what they're doing.
And I said it in language[br]that could be understood
by a natural scientist.
I described their bodies[br]in the terms of biology.
I describe the gravitational[br]effects on them
in the terms of physics.
I talk about them,
I talk about their brains in[br]the language of neuroscience.
I fill in all these details.
Is it, in principle, possible for me to
get to the point where there are
no further questions of the form
"You've left something out, tell me more"
to be asked.
Some people claim there is,
it is possible to get to this point.
Other people say it's[br]not, it's not possible
to get to this point.
However much I add, just detail,[br]detail, I add to the description,
there are gonna be aspects of reality
that are gonna remain undescribed.
So, here we'll look at an argument
to the effect that that's the case.
There are aspects of reality[br]that cannot be described
in the language of the natural sciences.
Here is a thought experiment[br]originally made up
by a philosopher by the[br]name of Frank Jackson.
Imagine a woman, Mary, who lives in a
black and white room.
A windowless room whose walls are white,
whose furniture is black.
A room that contains no colored things.
Imagine furthermore that Mary has
grown up in this room all her life.
She's never seen a colored thing.
Her hands are painted gray.
Her fingernails, black.
The food she eats is[br]white food or black food.
She's never seen anything that's blue.
She's never seen anything that's red.
She's only been confronted with
black or white or gray things.
Now, that's not to say
that Mary isn't a bit of an expert
when it comes to color.
Scientists have taught her
everything that they know about
the physics, chemistry, and biology
of colored things and color vision.
So, for example, Mary knows,[br]with respect to redness,
she knows the reflective properties
of things that reflect red light.
She knows the chemistry of surfaces
that reflect red light.
She knows the wavelengths of light
such that we call light[br]of that wavelength red.
She knows what happens when[br]light of that wavelength
enters an eye,
the way in which it[br]passes through the cornea
and hits the retina.
She knows what goes on beyond that.
She knows everything[br]about the neurobiology,
the neuroscience, of[br]the perception of red.
We can imagine, indeed, we can
expand this thought experiment so that
she doesn't just know everything[br]that current scientists,
the scientists around us nowadays,
know about the vision of red.
She knows everything[br]that science of any kind,
any kind of language of natural science,
could ever communicate with respect to
the vision of red.
She is a perfect expert when[br]it comes to the science of red.
So, if you were to give her any kind of[br]exam,
she would ace it, when it comes to
the science of redness,
what it is to see a red thing.
Nonetheless, in spite[br]of all this knowledge,
it might seem as if there's something
that Mary doesn't know.
To illustrate that, we can
add to our thought experiment.
We can suppose that, for the first time,
Mary is about to be[br]confronted with a red thing,
a ripe tomato.
The scientists bring it in
underneath a kind of veil, a gray veil.
They put it on the table.
The scientists are themselves[br]painted perfectly gray,
wearing gray contacts.
With no trace of flesh on them at all.
They put the veiled object on the table.
Mary stands before it.
She's wondering, "What will it be like?
What will it be like[br]to see the red tomato?"
The veil is lifted.
She gasps.
There is the red tomato.
Now, one thing it would be very natural
for Mary to say in this context is
"Wow, I've just learned something.
I've learned what it's[br]like to see a red thing.
That was something I didn't know before."
Let's suppose that's right.
If that is right, then it would seem
as if there's stuff to know[br]that can't be described
in the language of the natural sciences.
That's what's nowadays know as
The Knowledge Argument for thinking
that there are aspects[br]of the world that can't
be described in the language[br]of the natural sciences,
that are nonphysical.
That example was quite elaborate.
We didn't need quite such an[br]elaborate thought experiment.
Just as Mary doesn't know[br]what it's like to see red
or what it's like to see blue
before she actually sees a red thing
or sees a blue thing,
so one might think that somebody who
doesn't know what it's[br]like to taste coffee
doesn't know what it's like to taste[br]coffee prior to tasting
coffee for the first time.
No matter how much
they learn about the science of taste.
Let's try to put this[br]argument, what I just said,
in a slightly more[br]rigorous and careful way.
We'll put it in terms of an argument
with premises and conclusions.
Okay, premise one of the argument is this:
before drinking the[br]coffee, you know all facts
that are describable in the[br]language of natural sciences.
Seems pretty good.
Everything that a[br]scientist could tell you,
you already knew.
Premise two:
after drinking the coffee[br]for the first time,
you learned a new fact.
That seems good as well.[br]
you're like, "Whoa,
that's what it's like to drink
coffee. I always wondered.[br]That's something I now know:
what it's like to drink coffee."
Conclusion:
there's some fact that's not describable
in the language of natural sciences.
And, it seems to follow
that any description of the world
that's purely done in the[br]language of natural science
is going to be incomplete.
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