Perception is how we humans come to know things about the world. We use our senses to gain
information about the external world, and we come to hold beliefs about it, which then
inform the actions we make. However, for such a basic aspect of our experiential lives,
the phenomenon of perception is also one of the most puzzling things about consciousness.
Just how exactly does the external world impress itself on our senses in such a way that we
come to form an inner conscious experience about what the external world is like? And
if there really is such a separation between our conscious experience and what goes on
outside it, then how can we ever know that our perception is giving us accurate information
about the external world at all? All these problems and more have got philosophers thinking
about just what perception is, so in this video, let’s take a look at some theories
of perception. And, for some added stakes, I will be taking a shot each time I fail to
prove the existence of the external world. I mean, I wrote this script, so I know fully
well how this will turn out, so this video is basically an excuse to get pissed. Look,
it’s… it’s been a rough week, okay?
It all starts with a theory called direct realism. In direct realism, there are two
components involved in perception: the perceiver and the perceived object. When the perceiver
looks at something, for example this table, there is a direct and unmediated awareness
of this object, and it will continue to exist even when the perceiver looks away from it.
In other words, the perceived object exists in the world exactly as we perceive it. Direct
realism is the common sense theory that most people have about the world (unless, of course,
your intuitions have been destroyed in the industrial shredder that is a philosophy degree).
It’s in tune with our common sense, it avoids scepticism rather nicely, and it gives a clear
account as to how we come to know things about the world. We can be sure that trees are green,
sugar is sweet, and fleshlights are squishy, because all these objects actually have the
properties we perceive them to have. Simples, right?
Well, perhaps it’s a little bit too simple. Imagine that you’re sitting at the table
for your breakfast vodka and orange, and inside the glass is a straw. You might notice that
the straw appears bent. Of course, the straw is not bent in reality, but the refraction
of light makes the straw appear bent. This is a problem for direct realism, called the
argument from illusion. If we have a direct awareness of a bent straw, but the straw is
not bent in reality, then how direct can our perception really be? Another problem comes
with the argument from hallucination. Often when someone experiences a hallucination,
such as that tab of acid that’s just a tad bit stronger than advertised, it’s difficult
or impossible to tell apart the hallucination from a veridical perception. If the hallucination
is indistinguishable from a veridical perception, but the hallucination only exists within the
mind, then it follows that our normal perceptions must be within the mind as well. There are
even more problems for direct realism, such as perceptual variation (such as when a square
appears as a diamond when viewed from an angle) and the time-lag argument (how we can never
really have a direct awareness of the external world because light takes a certain amount
of time to reach our eyes, and even longer to be processed in the brain). It seems as
though perception is not as simple as direct realism claims, and that calls for my first
shot of this video.
Alright, so direct realism cannot demonstrate the existence of the external world, so let’s
examine a more complex theory of perception - indirect realism. Like direct realism, indirect
realism is a realist theory, which means that objects actually exist in the world. However,
there are now three components involved in perception: the perceiver, the perceived object,
and the appearance of the perceived object. When we look at the table, what we are directly
aware of is not the table itself, but rather how the table appears in our consciousness.
Our perceptions are separated into primary and secondary qualities. Primary qualities
resemble the actual qualities of the table, such as its size, shape, and mass. In other
words, if different scientists were to undertake a scientific investigation of the table, all
of them would agree on their measurements. However, secondary qualities, such as the
colour, texture, and smell, do not resemble the table. If we say the table is white, what
we really mean is that the table has the power to cause the sensation of white in us, but
that it’s not really white itself. In other words, the secondary qualities of the table
are mind-dependent, because a consciousness is required in order to experience them. So
the next time someone asks you if a tree falling in the woods with nobody around to hear it
makes a sound, tell them to firstly piss right off, and secondly no, because sound is a secondary
quality and is therefore mind-dependent. So, this seems like a better theory. Has the external
world been shown to exist? Unfortunately not. Indirect realism essentially
drives a wedge between how objects appear to us and how they actually are. Although
this solves a lot of the problems that direct realism faces, it also creates some of its
own. Because indirect realism creates this distance between appearance and reality, called
the veil of perception, we can be sceptical about the existence of anything outside our
own consciousness. If we only have access to appearance, and appearance is mind-dependent,
then we can have no knowledge about stuff outside our minds, or whether anything exists
outside our minds at all. We can imagine, for instance, that some evil scientist has
plugged electrodes into our brains and is feeding us electrical impulses that mimic
the sound of birdsong, or the colours of the sunset, or the feel of the condom that’s
ribbed for her pleasure. This thought experiment is called the brain-in-a-vat, a modern version
of the Cartesian evil demon. And if something like this is theoretically possible, then
it seems as though indirect realism has been ruled out too. You know what that means…
it’s time for me to take another shot and you to watch my life slowly fall apart.
So, both direct and indirect realism are bollocks, what’s next? Well, the last theory we will
examine is called idealism, and it’s a little bit more radical than the other two. In idealism,
there are only two components involved with perception: the perceiver and ideas. You might
have noticed that idealism drops the realist name, and this is because with idealism, there
are no such things as mind-independent objects that exist in the world, only ideas. Er, what?
Basically, idealism tries to collapse the primary/secondary quality distinction that
indirect realism established, and it does this using quite an ingenious thought experiment.
Imagine, once more, our table. But this time, let’s remove all its sensible qualities.
Subtract the colour, texture, taste, smell, and sound. What’s left once we have this
invisible, intangible, tasteless, unsmellable, and silent table? Well, nothing really, and
that’s exactly the point. Without the sensible secondary qualities, we are left with no access
to the table at all. Therefore, all we have access to are ideas inside our own minds,
and there are no such things as objects in an external world. For the idealist, the whole
world is mind-dependent. Great, the table and the external world exist
inside my consciousness as ideas; is the video over yet? Not quite, I need the ad revenue
in order to eat. Even though it seems like the idealists have been smoking DMT with Joe
Rogan, their theory is actually more simple than both direct and indirect realism. By
eliminating matter, there is one less assumption we need to make when it comes to perception,
and according to Ockham’s razor, the simplest solution is often the better one. If you are
wondering what reason we have to prefer ideas over matter, the idealist would respond by
asking what reason we have to prefer matter over ideas. Both assumptions are equally absurd,
and if we do not need to worry about the external world in idealism, then it’s really the
more efficient theory. However, there is still an issue here. If the external world is merely
an idea inside the mind, then idealism seems to lead us straight into solipsism, and we
can doubt the existence of anything besides our own consciousness. Your hands, your dog,
and even other people, might be figments of your imagination. Idealism can be rescued
if we appeal to the existence of God, but since most philosophers nowadays are a little
hesitant to do that, it’s generally assumed that idealism still leads us into solipsism,
and we become trapped inside our own mind, shut off from the rest of the world. So, the
external world still doesn’t exist, and that calls for my third and final shot.
So, where does this leave us? Well, after this brief whistle-stop tour over the various
theories of perception, I think we can be reasonably sure that the external world exists
in some form or another. Philosophers have offered various arguments about the existence
of the external world, such as how we have little control over what we actually perceive.
No amount of conscious effort can stop the perception when you walk in on your parents
mid-shag, and if our perception was really the result of our own conscious activity,
then it really seems like we would be able to do something about it. Even though we cannot
be absolutely certain about what exists outside our own minds, the best explanation is that
our senses and nervous system have allowed us to track the environment with a fair amount
of accuracy, otherwise our chances of survival would be very unlikely. Scepticism is all
well and good, but it’s the difference between a razor and a butcher’s knife when having
your morning shave. They’ll both get the job done, but one’s just a little better
for the job than the other. There is still much more scientific investigation to be done
on just how our perception works, but until that time when we know for certain, you never
know… you could just be a brain in a vat, drifting around space, having all your sensations
fed to you through wires. Thank you very much for watching, peace and love, and I’ll see
you in the next video.