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Here is something obvious that maybe you've never stopped to think
about. Things are made up of other things.
This bouncy ball is made up of rubber. This brick building
is made up of brick, glass, steel and lots of other things.
Now it turns out that this plain, everyday fact—
that things are made up of other things— is actually quite mysterious.
Think about the ball again. What is this thing?
Is it a ball? Or is it really just a round hunk of rubber...
and we call it a ball? Or consider this thing again.
Is it a building? Or really just a bunch of brick, glass, and steel?
Now, you might get impatient with this kind of thing and say, "Look, this isn't
hard: it's a building! And the building just *is* a collection of
brick, glass, and steel. In other words, the building and the
materials it's made of are the same thing. But philosophers have
known for over 2,000 years that the answer is not so simple.
For instance, what if the building falls down?
We still have the brick, glass, and steel. So if the building just
is the materials it's made of, then this pile of rubble...
is the building! But that doesn't seem right.
It's not a building anymore, is it? Same goes for the bouncy ball. You might
want to say, "Oh come on! The ball just is the hunk of
rubber." But if we shredded the ball into a
little pile of rubber shavings it wouldn't be a ball anymore, would it?
But it would still be the same bit of rubber.
What in Sam Hill is going on here?! Welcome to what philosophers call
The Puzzles of Material Constitution. "Material"
because these are puzzles about physical objects.
And the word "constitution" is just a fancy way of saying
"being made up of" as in the hunk of rubber
constitutes the ball and the brick, glass, and steel
constitute the building. Philosophers who study material constitution
are interested in how it is that physical things
make up other physical things. As we've seen,
it's not so straightforward. Let's look at three
famous puzzles that illustrate the problems of material constitution.
This is Tibbles. This is Tib. Tibbles. Tib. You see, Tibbles
is just a regular old cat. But Tib is the name that we've given to this
large part of Tibbles. In other words, Tib is a cat-part.
The part of Tibbles that includes everything except the tail.
So we have two different physical things here:
Tibbles the regular old cat and Tib, a large tail-less part of Tibbles.
But now imagine that Tibbles loses her tail in a terrible accident.
Obviously, Tib is just fine. In fact, nothing happened to Tib at all!
Because Tib never had a tail in the first place. But what about Tibbles?
Did Tibbles survive the loss of her tail? Well, if we say she did, then Tibbles and
Tib are both right here! In other words,
two different physical things—Tibbles and Tib—are
occupying the exact same physical space. But that can't be, can it? So maybe it's
best to conclude that Tibbles passed away with the loss of her tail
and only Tib remains. But if we apply this same reasoning to
human beings, well, then we must conclude that nobody
survives the loss of a body part. When Bob loses a body part he doesn't
survive!
Here is the ship of Theseus sailing the ancient Mediterranean.
Every once in a while repairs must be made at sea.
Perhaps one day an old wooden plank is tossed overboard and replaced.
Maybe another day a frayed length of rope is discarded, or a bit of sail,
and replacements are brought out from the supplies. This goes on over several
years until every single piece of the ship has been
replaced. Question: is this still the same ship of
Theseus that left port several years ago? Or is
it a different ship? If it's a different ship, at what point
did it stop being the old ship? And what if I told you that a crew of
sailors has been following along behind, collecting all the discarded items and
they have now rebuilt an entire ship from the parts
that were thrown overboard. Is this the ship of Theseus?
It's 9 am and this is a lump of play-doh. Now it's 9:07am and I have sculpted the
lump of play-doh into a sculpture. Let's call the
sculpture, Frosty. Now as you look at Frosty on my desk we
can ask, "Where did the lump of play-doh go?" Then
you might answer— in sort of an exasperated tone—"It didn't
go anywhere, it's right here! Frosty just is the lump of play-doh and
the lump of play-doh is just Frosty." But there's something very fishy about
this answer. For one thing, the lump of play-doh
existed at 9am but Frosty didn't. How can you say
Frosty just is the play-doh, if they came into the
world at different times? Or what about this:
the lump of play-doh can survive my squashing it.
See? It's still a lump of play-doh. But poor old Frosty has gone away. How
can one survive and not the other, if they're just the
same thing?
We might have to go back and say they're not the same thing. This is a lump of
play-doh AND it's Frosty. But that means we've
arrived at the conclusion that two different physical objects can
overlap each other in the exact same physical space. Are we
really ready to say that there are two cats here:
Tibbles and Tib? Now you might feel like you've been
tricked or we're just playing word games here.
But if you think about it hard enough, and maybe re-watch the video,
I think you'll see that there are real questions here. And we're trying to get
at the truth about the nature of physical objects.
It's a classic example of metaphysics. Of course, I haven't offered any
solutions here. You'll have to stay tuned for that.
But at least now you know that the boring old world of tables and chairs,
bouncy balls and buildings, is more mysterious
than you thought.
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