Epistemology: Science, can it teach us everything?

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Epistemology: Science, can it teach us everything?발음듣기

(intro music) Hi, my name is Caspar Hare.발음듣기

I'm a professor at MIT, the Massachusetts Institute of Technology.발음듣기

Today we're going to talk about science.발음듣기

Can it teach us everything there is to know about reality?발음듣기

Science is an impressive thing. Scientists have, for hundreds of years, been able to predict the movements of comets, the eclipses, and the like, decades in advance.발음듣기

In the 20th century, scientists were able 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 achieve in the 21st century.발음듣기

There's an issue though. Just how impressive, or how good, is science at describing the world that we live in?발음듣기

One strong claim that we might make is that science can give a complete description of reality.발음듣기

It can describe everything that there is to know or be known about the world.발음듣기

Now, at various points in history, people have disputed this.발음듣기

They've thought however impressive science was, there would be no way that it could give a complete description of reality.발음듣기

There would be things like angels, spirits, and the like that could not be described in the language of science.발음듣기

Today, what we'll do is we'll look at a modern argument to this effect.발음듣기

To the effect that are aspects of reality that cannot be described in the language of science.발음듣기

Our first job is to explain what it is for a description of an aspect of reality to be complete.발음듣기

We'll do this by way of an example.발음듣기

Here's a description of what's going on in a room (it happens to be this room): there are three people in the room.발음듣기

End of description. Was that a good description? Well, you might think that there are things that the description left out.발음듣기

I said there were three people in the room.발음듣기

I didn't say anything more about them.발음듣기

I didn't say whether they were standing up, sitting down, whether they were riding on little horses around the room.발음듣기

There were bits that my description left out.발음듣기

I could have told you more.발음듣기

I could have said, "There were three people in the room, sitting around a table."발음듣기

End of description. Still, my description would have been incomplete.발음듣기

I didn't tell you their names.발음듣기

Maybe they were called Ben, Balthazar, Fitzgerald.발음듣기

Maybe they were called, as they actually are called, Damien, Gaurav, and Caspar.발음듣기

Let me add that to the description.발음듣기

That their names are Damien, Gaurav and Caspar.발음듣기

They're sitting around a table, in this room.발음듣기

Still, there's lots that I've left out.발음듣기

I haven't told you what they're wearing, I haven't told you anything about their heights, about their ages, about all kinds of things concerning these people.발음듣기

These are all details that I could fill in.발음듣기

Suppose I went on, and I added layer upon layer of detail to the description, I said more and more about the people in this room, what they're doing.발음듣기

And I said it in language that could be understood by a natural scientist.발음듣기

I described their bodies in the terms of biology.발음듣기

I describe the gravitational effects on them in the terms of physics.발음듣기

I talk about them, I talk about their brains in the language of neuroscience.발음듣기

I fill in all these details.발음듣기

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.발음듣기

Some people claim there is, it is possible to get to this point.발음듣기

Other people say it's not, it's not possible to get to this point.발음듣기

However much I add, just detail, detail, I add to the description, there are gonna be aspects of reality that are gonna remain undescribed.발음듣기

So, here we'll look at an argument to the effect that that's the case.발음듣기

There are aspects of reality that cannot be described in the language of the natural sciences.발음듣기

Here is a thought experiment originally made up by a philosopher by the name of Frank Jackson.발음듣기

Imagine a woman, Mary, who lives in a black and white room.발음듣기

A windowless room whose walls are white, whose furniture is black.발음듣기

A room that contains no colored things.발음듣기

Imagine furthermore that Mary has grown up in this room all her life.발음듣기

She's never seen a colored thing.발음듣기

Her hands are painted gray. Her fingernails, black.발음듣기

The food she eats is white food or black food.발음듣기

She's never seen anything that's blue.발음듣기

She's never seen anything that's red.발음듣기

She's only been confronted with black or white or gray things.발음듣기

Now, that's not to say that Mary isn't a bit of an expert when it comes to color.발음듣기

Scientists have taught her everything that they know about the physics, chemistry, and biology of colored things and color vision.발음듣기

So, for example, Mary knows, with respect to redness, she knows the reflective properties of things that reflect red light.발음듣기

She knows the chemistry of surfaces that reflect red light.발음듣기

She knows the wavelengths of light such that we call light of that wavelength red.발음듣기

She knows what happens when light of that wavelength enters an eye, the way in which it passes through the cornea and hits the retina.발음듣기

She knows what goes on beyond that.발음듣기

She knows everything about the neurobiology, the neuroscience, of the perception of red.발음듣기

We can imagine, indeed, we can expand this thought experiment so that she doesn't just know everything that current scientists, the scientists around us nowadays, know about the vision of red.발음듣기

She knows everything that science of any kind, any kind of language of natural science, could ever communicate with respect to the vision of red.발음듣기

She is a perfect expert when it comes to the science of red.발음듣기

So, if you were to give her any kind of exam, she would ace it, when it comes to the science of redness, what it is to see a red thing.발음듣기

Nonetheless, in spite of all this knowledge, it might seem as if there's something that Mary doesn't know.발음듣기

To illustrate that, we can add to our thought experiment.발음듣기

We can suppose that, for the first time, Mary is about to be confronted with a red thing, a ripe tomato.발음듣기

The scientists bring it in underneath a kind of veil, a gray veil.발음듣기

They put it on the table.발음듣기

The scientists are themselves painted perfectly gray, wearing gray contacts.발음듣기

With no trace of flesh on them at all.발음듣기

They put the veiled object on the table.발음듣기

Mary stands before it. She's wondering, "What will it be like?발음듣기

What will it be like to see the red tomato?"발음듣기

The veil is lifted. She gasps.발음듣기

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.발음듣기

I've learned what it's like to see a red thing.발음듣기

That was something I didn't know before."발음듣기

Let's suppose that's right. If that is right, then it would seem as if there's stuff to know that can't be described in the language of the natural sciences.발음듣기

That's what's nowadays know as The Knowledge Argument for thinking that there are aspects of the world that can't be described in the language of the natural sciences, that are nonphysical.발음듣기

That example was quite elaborate. We didn't need quite such an elaborate thought experiment.발음듣기

Just as Mary doesn't know 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 like to taste coffee doesn't know what it's like to taste coffee prior to tasting coffee for the first time.발음듣기

No matter how much they learn about the science of taste.발음듣기

Let's try to put this argument, what I just said, in a slightly more rigorous and careful way.발음듣기

We'll put it in terms of an argument with premises and conclusions.발음듣기

Okay, premise one of the argument is this: before drinking the coffee, you know all facts that are describable in the language of natural sciences.발음듣기

Seems pretty good. Everything that a scientist could tell you, you already knew.발음듣기

Premise two: after drinking the coffee for the first time, you learned a new fact.발음듣기

That seems good as well. you're like, "Whoa, that's what it's like to drink coffee. I always wondered.발음듣기

That's something I now know: what it's like to drink coffee."발음듣기

Conclusion: there's some fact that's not describable in the language of natural sciences.발음듣기

And, it seems to follow that any description of the world that's purely done in the language of natural science is going to be incomplete.발음듣기

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