Perception as a source of knowledge
Theories of perception:
-According to theories of perception, we acquire knowledge of the external world through our
senses. Perception means getting as awareness of the world using our 5 senses. This makes
theories of perception empirical in nature – verifiable by observation or experience.
However, a problem with empiricism is that it falls prey to scepticism – our senses can deceive us-
we don’t know whether the perspective of the world given to us by our senses is real or not.
Examples showing that our perception of the world doesn’t necessarily match what the real world
(independent of our experiences) is like:
- A straight stick in water looks bent, the stick doesn’t physically bend; it is an optical illusion
resulting from the physical process of refraction.
- How do I know that objects exist when I don’t perceive them? Eg If a tree falls in the forest
and no one is around, does it make a sound? I actually have no physical, empirical proof that
the tree falls or that it makes a sound. I can check that the tree is still there but cant check
after it falls that it has made a sound.
These are all representations of reality that do not match reality. HUGE PROBLEM for empiricists as
the starting point of empiricism is that perception can give us a true understanding of the world.
Although, if empiricists can explain these phenomena philosophically, according to what we can
actually know of the world, they can answer sceptical attacks effectively.
-Theories of perceptions try to solve problem of objects existing when we don’t perceive them. It
seems absurd to deny that they do – eg I know my house will still be there when I come home. But at
the same time, if the beliefs we have about the world depend on our interaction with the world
through our senses, then if no one actually interacts with some objects in the world, there is no way
of us proving that they exist. IMPORTANT PROBLEM.
Realism- the belief that there is an external world independent of my perception.
Anti-realism- belief that the world I perceive is the only world there is, there is no world outside of
my perception.
Direct Realism - The immediate objects of perception are mind-independent objects and their
properties
-Is a one-world view; it argues that our perception of the world is unmediated – we see, smell, hear
and taste things directly as they are, there is no third thing mediating between the person who
perceives and the physical object they perceive so DR rejects the indirect realist notion of ‘sense
data’. Our awareness of the physical world is direct and the world exists with all its properties intact
outside the mind, it is mind-independent. Coffee possesses the bitterness we perceive it to have. We
immediately perceive physical objects if there is nothing mediating between perceiver and
perceived.
-The reason we see the world when we open our eyes is because the world is there: there is a casual
relation between the world being there and us seeing it when we open our eyes. It would be absurd
to argue that objects disappear when we don’t perceive them.
-Objects in the world are the cause of our perception. We have the sense-experience of coffee
because we are drinking coffee and a liquid called coffee exists and gives us that sensation.
,-DR explains why we all agree that some of the material objects in this room are tables and that the
particular colour of the wall is yellow.
-All the qualities of an object are in the object: when I perceive the object, I therefore perceive its
properties eg an apple is red, round and crunchy regardless of whether I perceive it or not.
Strengths of Direct Realism:
-It’s in tune with common sense. Russell argues we should accept the common-sense opinions and
beliefs we are inclined to by instinct, unless they lead to inconsistency.
-It avoids scepticism: it gives us a clear account of how it is that we come to have knowledge of the
world: we know about it because our senses provide immediate access to its true nature.
-It has explanatory power. For if it is true that I am directly aware of physical reality and its
properties, this explains why I am able to execute a whole range of practical actions on a daily basis
eg finding food that I need to survive.
-Explains why I perceive what I do. I see the tree as green because the tree is green. My perception
of the tree is regular and predictable precisely because there exists a real tree beyond my mind
which causes my perception of it. I have no control over what I see when I open my eyes, because
there really are mind-independent objects causing me to perceive.
-Explains why we agree about what we perceive and is in tune with our sense that we occupy the
same universe as everyone else.
Problems associated with Direct Realism – there suggest that we don’t see the world directly;
rather, we see a perceptual representation of the world.
The problem of perceptual variation ON SPEC
-Russel looks at a table and decides to study its features. What he realises goes completely against
the claims of direct realists. The table changes colour and shade depending on his angle of sight, at
times it is dark brown, at other times lighter. It also changes shape from a rectangle when viewed
from directly above to a non-rectangular quadrilateral from other perspectives. Does this mean that
the table has different colours and shapes, that it physically changes?
-What he concludes is that we must distinguish between appearance and reality, but because we
only have access to how objects appear to us, can we ever know the real object?
-Russel calls what appears to us in experience sense-data. And says that the sense-data (i.e colour
and shape of table as the viewer sees it under particular circumstances) is distinct from the table
itself. The table exists independently of the viewer’s perception of it.
DIRECT REALISTS REJECT THE IDEA OF SENSE-DATA AND RUSSELL’S ARGUMENT THATWHAT WE
PERCEIVE DIRECTLY IS SENSE-DATA. We don’t perceive the appearance of a table, what we see is a
table. Direct Realists don’t argue that the table changes; some of its properties may appear to
change but in itself it doesn’t. The science of optics can explain why the table appears to change.
Another example of perceptual variation which disproves the direct realist claim that the world is as
I perceive it:
, -If the world is exactly as it appears to my senses, this means that when objects move away from
me, they get smaller. EG, if I stand on top of a high building and look down at the street, my car will
look as tiny as a toy car. As a direct realist, I will have to say that my car has physically changed size!
THIS SHOWS, that DR doesn’t follow but rather defies common sense. Because of perspective the
world cannot be exactly as it appears to us.
Problem of perceptual variation in premises using coin example:
P1) For direct realists, the reason why a coin appears circular when perceived is because the coin has
certain properties – in this case, circularity.
P2) If a perceiver is immediately aware of an object having a property, that means the object has
that property.
P3) However, if another perceiver looked at the coin from a different angle, the coin would look
elliptical.
C1) That means, if P2 is true, the coin must also be elliptical.
P4) However, the coin cannot have the properties of being circular and elliptical at the same time.
C2) Therefore, P2 is false: we do not directly perceive physical objects.
Russell then concludes that:
-The immediate objects of perception are sense data.
-We must infer the existence and the real properties of objects on the basis of direct acquaintance
with the sense data.
-so, we do not perceive the world directly.
The problem of relative sensations
-Raised by Berkeley.
-In his first Dialogue, Berkeley has Philonous ask Hylas what happens if you put a hot hand and a cold
hand into the same bucket of lukewarm water. The water will feel cold to one hand and hot to the
other. However, the same area of water cannot really be both hot and cold at the same time.
-His conclusion is that it only appears to be hot and cold. Heat and cold are not properties of the
objects; they are the effects the object has on observers like us.
-Berkeley’s conclusion is stronger than Russell’s. Russell doesn’t deny that objects have real
properties, only that we don’t perceive them directly as they are. Berkeley’s conclusion is that the
perceived qualities of objects are in the mind, rather than in the objects.
Response to issue of Perceptual Variation
-The argument attacks the assumption of direct realism (that we perceive the properties of objects
as they really are). But the direct realist can give up this rather naïve assumption without necessarily
giving up direct realism. The direct realist can accept that objects may appear differently to
perceivers and yet insist that they are nonetheless directly perceived.
