Transcript What Is It Like To Be a Bat?”

“What Is It Like To Be a Bat?”
Depth Perception
The world (visually) appears to us as though it is
three-dimensional.
Some things appear closer to us and others
farther away.
This is true even though all the light our eyes
receive is projected on a 2D surface (the retina).
Retinal Projection
Stereopsis
There are lots of clues the brain uses to figure
out depth relations.
Obviously, for example, objects that occlude
other objects must be closer.
But the most powerful way of determining
depth relations is geometrical calculation.
Stereopsis
Comparing the two retinal images, if the angle
between the fixation point and the image of
some other object is equal, then the object lies
in the Veith-Muller Circle.
If there is a difference in the angle, we can use
geometry to compute how far away from the
circle the object is.
Auditory Localization
While hearing is in lots of ways different from
vision, there are some very general similarities.
How can we tell that a sound is to our right
rather than our left? It reaches our right ear
first. Differences in the time it takes for sounds
to reach our ears gives us information about the
location of sound sources.
Archonta
Bat Echolocation
Bats, like their cousins (us), have the ability to
spatially localize sound. They’re just much better
at it than we are.
They make a high-pitched sound that echoes off
objects. Listening to the echo, the bat can
calculate where an object is, how big it is, and
which direction it’s moving in.
Bat Sonar
“WHAT IS IT LIKE TO BE A BAT?”
What Conscious Experience Is
“The fact that an organism
has conscious experience
at all means, basically,
that there is something it
is like to be that
organism.”
What Conscious Experience Is
“[the expression ‘what it is
like’] does not mean ‘what
(in our experience) it
resembles,’ but rather
‘how it is for the subject
himself.’” n. 6
What Is It Like To Be a Bat?
It’s reasonable to think that bats, being
intelligent mammals that are closely related to
human beings, have conscious experiences.
Therefore, there is something that it is like to be
a bat.
What Is It Like for Me To Be a Bat?
“[T]ry to imagine that one has webbing on one's
arms, which enables one to fly around at dusk
and dawn catching insects in one's mouth; that
one has very poor vision, and perceives the
surrounding world by a system of reflected highfrequency sound signals; and that one spends
the day hanging upside down by one's feet in an
attic…”
What Is It Like for Me To Be a Bat?
In so far as I can imagine
this (which is not very far),
it tells me only what it
would be like for me to
behave as a bat
behaves…”
What Is It Like for a Bat To Be a Bat?
“But that is not the question. I want to know
what it is like for a bat to be a bat. Yet if I try to
imagine this, I am restricted to the resources of
my own mind, and those resources are
inadequate to the task. I cannot perform it
either by imagining additions to my present
experience, or by imagining segments gradually
subtracted from it, or by imagining some
combination of additions, subtractions, and
modifications.” – Nagel
Points of View
“My point is not that we cannot know what it is
like to be a bat. I am not raising that
epistemological problem. My point is rather that
even to form a conception of what it is like to be
a bat… one must take up the bat’s point of
view.” – Nagel n. 8.
Points of View are Types
I do know what it’s like to be you (in some
sense).
I don’t have any of your experiences but I have
the same type of experiences, and I can use
those to understand your experience.
But I don’t have the types of experiences bats
have.
Radar Analogy
The radar at HKIA has a certain “perspective.” It
represents planes flying in and around Hong
Kong.
The radar at JFK has a different “perspective.” It
represents planes flying in and around NYC.
But I could take the radar machine at HKIA and
install it at JFK and there would be (in some
sense) no difference in operation.
Speedometer Analogy
Imagine two speedometers: one that simply
says “fast,” “slow,” or “normal,” and one that
registers speeds in kph.
I can’t replace one for the other and get the
same results. They “subjectively” have different
types of “experiences.”
Objectivity
Giving a scientific account of something involves
removing talk about how it (phenomenally)
appears.
Describing how current flows through a
transistor tells us nothing about how it appears
to any particular creature, and doesn’t require
any particular senses to understand.
Objectivity
This means that any individual can investigate
this (or any other scientific phenomenon) from
any point of view at all.
Difference with the Mental
You can understand brain states objectively,
from many points of view.
Blind people have no barrier to being
neuroscientists.
But blind people cannot know what it is like to
see red.
Can’t “Objectify” Experience
The reason is that what we are trying to do in
understanding experience is finding out what it
is like from a perspective (e.g. what it is like for a
bat to be a bat).
This means that we cannot remove perspectives
from our discussion… we cannot be objective.
Note
Nagel believes in the objectivity of experience in
the following sense: he thinks there are facts
about conscious experience, and about which
things are experiencing what. These facts exist
independently of whether we can ever imagine
or know them. They are “objective” facts. They
are subjective in the following sense: you need
to have a particular point of view to think about
these facts.
Main Argument
• Even thinking about certain conscious facts
requires us to take a particular point of view.
• Physical/ scientific investigation requires us to
abstract from particular points of view.
• Thinking about/ discussing consciousness is
not something we can do with our ordinary
scientific tools.
• [This does not mean they are not physical
facts.]
Objection: Imaginative Ability Not a
Further Fact
One main objection against Nagel is the claim
that what we can imagine is not a good guide to
what exists.
Suppose I can’t imagine a 1,000,000 sided
figure. That doesn’t show that there’s no
physical explanation for being a million sided
figure.
Objection: We Can Imagine What It’s
Like To Be a Bat (Or an Alien).
Some philosophers have even argued that I can
imagine what it’s like to be a bat.
I can easily imagine what it’s like to hear a sound
to my right.
Can’t I imagine hearing it at a particular point,
moving in a particular direction, to my right?