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On September 13, 1848, a freak accident caused an explosion

that drove an iron rod straight into the skull of a worker named Phineas Gage.

A metal rod almost as tall as he was went through his skull – and he didn’t die.

But, the Phineas from before the accident, and the one who lived after it, didn’t seem to have a lot in common, personality-wise.

The Phineas with no hole in his brain was a proper, hard-working gentleman.

And the Phineas with the injured brain was, uh, sort of a belligerent jerk.

Phineas’ brain was changed – and his personality changed too.

This misfortune has provided lots of fodder for researchers of psychology and neurology.

But the case of Phineas Gage holds lessons for philosophers too.

It provides us with some rare, hard evidence that a part of us that's historically been thought of as non-physical

– our personality – is actually, directly affected by what happens to us physically.

Which raises the question: Where does our mind reside?

[Theme Music]

Now, not a lot of contemporary scientists would be all that surprised that an injury like the one Gage suffered could cause such a radical change.

That's because the dominant view held in much of Western science is what we call reductive physicalism.

This is the view that the world is made only of physical stuff, including us.

By this logic, everything about me, and you, can be explained in terms of our bodies

– our brains, hormones, and neurotransmitters.

So if everything about Phineas’s personality could be explained in terms of his brain,

it’s no shock that a radical change in his brain would bring about a radical change in his personality.

This same belief is at work when a psychiatrist prescribes antidepressants to a patient.

Change the patient's brain chemistry, change the patient's mood.

Now, physicalism may be the default scientific position, but remember, way back in episode 5,

our old friend Rene Descartes introduced us to cogito ergo sum – I think, therefore, I am.

Descartes believed that he could cast doubt on the existence of his body, but not the existence of his mind.

The fact that he could doubt one but not the other told him that he must be made of two different kinds of stuff.

This view, known as Substance Dualism, says that the world is made of both physical stuff and mental stuff.

Substance dualists say that minds are a separate, nonphysical substance that cannot be reduced to,

or explained in terms of, physical stuff, like brains.

And in this view, some things – like God – are pure mind, and other things – like rocks – are pure matter.

But humans, well, we’re kinda special.

We’re the only kind of thing that combines both stuffs in one being – both body and mind.

What’s more, these two substances appear to interact with each other inside of us.

This is called interactionism.

When I “make up my mind” to do something,

I have the power to compel my body to do as I please –

to get up off the couch and make myself a nice pb and j, for example.

What’s more, my mental states seem to have the ability to affect my physical states even against my will.

You ever notice how many people who are grieving or under a lot of stress, for example, often get physically sick?

Likewise, our bodies also appear to be able to affect our minds.

Like when you’re so hungry you just can’t focus on what your teacher is saying at all.

Or how a pure physical pleasure – like having a good cuddle with your cat – can pull you out of a bad mood.

Interactionists say that what's going on is that our two substances – minds and bodies – are interacting with each other.

But, if you think about it, this is actually a pretty puzzling proposition.

How can a purely mental thing have any affect on a purely physical thing?

The puzzle of how minds and bodies can interact with each other is known as the Mind-Body Problem.

This is the problem that makes us wonder:

How can my body have a separate entity called a mind lurking inside of it –

controlling it, and being controlled by it?

What would tether my mind to this body in particular –

why couldn’t my mind just go running off on its own, or take a dip into other bodies to see what it’s like in there?

Descartes’ answer, frankly, wasn’t all that satisfying.

He said that the mind is tethered to the body at the pineal gland – located at the base of the brain –

and that all mind-body interactions are filtered through that portal, if you will, between the mind and the body.

But that really only pushes the problem back, without solving it,

since the pineal gland is part of the physical body.

Many modern philosophers of mind, seeing no way to solve the mind-body problem,

have felt compelled to abandon substance dualism altogether.

Some are happy to be physicalists, but others are convinced that there are some parts of

human experience that simply can’t be boiled down to brains.

To see what they think is being left out, let’s head over to the Thought Bubble for some Flash Philosophy.

Contemporary Australian philosopher Frank Jackson presents us with the thought experiment of Mary,

a woman who has spent her entire life in a black and white room, learning everything via a black and white television.

While locked in this room, Mary becomes a neurophysicist specializing in the science of color.

She learns everything there is to know about light, optics, the physics of color,

and how it affects our sensory organs, but she has never seen it for herself.

So here’s the question:

When Mary finally walks out of the room and sees color for the first time, has Mary learned something new?

Jackson devised this thought experiment as an argument against reductive physicalism.

Because, Jackson says, the qualitative experience of seeing a color – say, red – isn't the same as knowing facts about red.

If everything could be explained in terms of the physical, then when Mary finally saw red,

it wouldn’t have contributed to her understanding at all.

It wouldn’t have told her anything that she didn’t already know.

Thanks, Thought Bubble!

What’s missing from a physicalist account, many argue, is what are known as qualia

– instances of subjective, first-person experience.

Qualia are what it feels like to stub your toe,

or take the first bite out of a slice of pizza,

or to learn that you have been deeply betrayed by a trusted friend.

It’s what Mary is said to gain when she steps out of the room and sees color for the first time.

Physicalists respond to thought experiments like Jackson’s by arguing that they beg the question.

Begging the question, you'll recall, is a philosophical fallacy in which the premises

assume the conclusion they’re supposed to be proving.

Jackson’s thought experiment assumes that Mary learns something new when she steps out of the room.

But, if physicalism is true, and if she really knows everything physical about color,

then of course seeing it for herself isn’t going to add to her understanding of it in any way.

Now, physicalists argue that their case is making progress,

as we learn more and more about the physical processes of the mind.

Well that’s not really satisfying, because we want an answer, not a promissory note.

But, to be fair, physicalists have only been at work for a few decades,

while dualists have been bashing their heads against the mind-body problem for centuries.

But not everybody falls cleanly into either the physicalist or the dualist camp.

The Mary case, and other arguments like it, convince some people that they have to maintain their commitment to dualism,

even though they can’t see a solution to the mind-body problem.

Some of those people adopt a view called epiphenomenalism.

This view says that physical states can give rise to mental states, but mental states can’t affect physical states.

So by this thinking, your beliefs, desires, and temperaments do exist,

but they have no power over anything physical about you.

Which might sound kind of weird and unconvincing.

But then there’s contemporary British philosopher Colin McGinn, who advocates a view called mysterianism.

This says that the question of consciousness is unsolvable by human minds.

It’s not that McGinn thinks we’re dummies.

He thinks humans are natural knowers – just give us a problem and we can figure it out.

But not this.

The reason, he says, is that our brains are compartmentalized.

The way we understand our mind is through reflection.

It’s deeply personal and subjective.

But the way we understand our brains and bodies is objective, and verifiable.

And those two modes of understanding just don’t mix.

No amount of reflection could lead to any claims about neurons firing,

and no amount of empirical research is going to give rise to what it’s like to see color through someone else’s eyes.

Our brains just don’t have a compartment that can piece together those different modes of evidence.

The mind-body problem hasn’t been solved, and physicalism hasn’t been proven, because

both of those things require our brains to do something they can’t do.

So what do you think?

Is your mind a separate substance, riding around in your body until it dies?

Can the complicated thing that is you – that thinks and feels and desires and hurts – be

reduced to a purely physical thing?

Did Mary learn something new? Is it possible to know?

Well that is up to your mind to figure out.

Today we talked about theories about where the mind resides.

We learned about reductive physicalism, substance dualism, and mysterianism.

And next time, we’re going to think about these issues some more,

with the help of some of my favorite kinds of potential persons – robots!

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Crash Course Philosophy is produced in association with PBS Digital Studios.

You can head over to their channel and check out a playlist of the latest episodes from shows like

Shanks FX, PBS Space Time, and BBQ with Franklin.

This episode of Crash Course was filmed in the Doctor Cheryl C. Kinney Crash Course Studio

with the help of these awesome people and our equally fantastic graphics team is Thought Cafe.