Uncertainty Provided by the Senses
Student Number: 250744090
February 28, 2014
Philosophy 1130G
Dr. Rachael Brown
Essay Question 1: “Our senses are an unreliable source of information about the world, and thus
can never provide us with any certainty in the truth of our beliefs.” Do you agree or disagree
with this statement? Why?
In this essay I will argue that our senses are an unreliable source of information about the
world, and as a result can never provide us with any certainty in the truth of our beliefs. First, I
will argue that our senses can be deceived by illusions and that this means our senses are
unreliable. I will then provide an objection to my argument on illusions and my response to that
objection. Next, I will argue that hallucinations show that our senses cannot provide us with any
certainty in the truth of our beliefs. An objection to this argument and my response to the
objection will then be presented. Lastly, I will argue that our senses are unreliable due to the fact
that we are only able to see objects as they were in the past and that this results in a lack of
certainty in our beliefs. I will then provide an objection to this argument and my response to the
objection.
For the purpose of clarity I will now state how I define some of the key terms used in this
essay. When I say our senses are an ‘unreliable’ source of information I mean that they are not
able to be trusted to provide what is likely true or correct (Merriam-Webster 2014). Also, when I
refer to our ‘senses’ I mean touching, seeing, hearing, tasting, and smelling which allow humans
to receive information about the world (Merriam-Webster 2014). Lastly, when I refer to
1
individuals perceiving objects I take ‘perception’ to mean the awareness of things by touch,
sight, hearing, smell, and taste (Crane 2011).
Humans experience illusions which are instances where either an object appears
differently to a given observer under different conditions or multiple observers perceive an
object in a different way (Ayer 1956, 87). In both cases, the senses are providing the observers
with false information about the world. I believe that this clearly shows that our senses can be
deceiving at times which makes them an unreliable source of information. Consider the example
of a coin that looks round to one observer and at the same time looks elliptical in shape to
another who is looking at it from a different angle. The observer who is seeing an elliptically
shaped coin is perceiving the coin differently than it actually is (Ayer 1956, 87-88). This means
that they are being deceived by their senses and thus, the senses are unreliable. Additionally, the
observer has no way of knowing whether or not they are receiving false information from their
senses which leads to the possibility that the observer is in a constant illusionary state. Therefore,
I believe this shows that the senses cannot provide us with any certainty in the truth of our
beliefs.
One objection to this argument is that despite the fact that objects may appear differently
to different observers under different conditions (illusions occur), over time one of these
perceptions will likely be what the majority of observers perceive and will be accepted as the
correct perception. This would allow for accurate information to be determined by the senses.
My response to this objection is that all of the different perceptions of an object over time may
never actually provide an accurate account of the given object, despite one particular perception
being the most common. Therefore, it is possible that no accurate information is ever acquired
2
which makes the senses unreliable and unable to provide us with any certainty in the truth of our
beliefs.
Secondly, it is possible for humans to hallucinate which occurs when a physical object
which is not actually present is perceived by a person. The person would clearly be receiving
incorrect information about the world from their senses because their senses would be telling
them that an object is present when it actually is not (Ayer 1956, 90). I believe that this shows
that our senses are an unreliable source of information. An example of a hallucination is when a
dagger is perceived by Macbeth. He is the only one that sees the dagger. This incorrect
observation seems exactly the same to Macbeth as other experiences he has had in the past. So,
despite the dagger not actually being present, Macbeth has no way of knowing that this is the
case (Ayer 1956, 90). This example provides support for my argument that the possibility of
hallucinations results in our senses being unreliable. It also highlights the fact that one cannot tell
whether or not they are hallucinating which means that certainty in the truth of our beliefs being
obtained from the senses is not possible.
An objection to this argument on hallucinations is that although it is possible for humans
to have hallucinations, it does not mean that they happen frequently. So, our senses can still be a
reliable source of information for the most part. I respond to this objection by explaining that the
fact that there is the possibility of hallucinations implies that it is possible for everything one
perceives to be part of a constant hallucination. We cannot be sure that we are not in this
situation, therefore, our senses cannot be a reliable source of information about the world
(Descartes 1986, 13). It follows that our senses cannot provide us with any certainty in the truth
of our beliefs because of the possibility of false information being collected.
3
Lastly, I will argue that our observation of any object is an observation of the object at a
previous time which makes our senses unreliable in providing accurate information about the
present. Since it takes time for light to travel over a distance, physical objects are not seen by
humans as they really are at the time at which humans see them. Instead, physical objects are
seen only as they were at some time in the past (Ayer 1956, 93). An object may have changed by
the time we perceive it which would make our observation of that object at the present time
inaccurate. This shows that our senses are an unreliable source of information about the world.
One example that I believe effectively portrays this argument is our observation of the sun. We
only observe the sun as it was eight minutes before the present time due to the large distance the
light must travel. By the time we see the sun, it may have undergone some massive change, such
as ceasing to exist, which means false information would be provided to us by our senses about
the current state of the sun. Other stars that are much further away from us than the sun are only
able to be observed as they were a much longer time ago which also shows how unreliable our
senses are in providing accurate information about the present (Ayer 1956, 94). Clearly, a failure
to provide accurate information about the world does not allow our senses to provide any
certainty whatsoever about the truth of our beliefs.
What I believe to be a strong objection to this argument is that while we may only
perceive distant objects, where light must travel a long distance, as they were in the past, the
cases where the distance travelled is negligibly small can provide observers with information that
is accurate and reliable. My response to this objection is that since it is possible for false
information about a distant object to be provided to us (when it takes longer for light to travel
from object to observer), we cannot justifiably say that accurate information is obtainable in
cases where a negligibly small time interval exists. This is because, “…the comparative length of
4
the interval makes no difference to the character of our experience…” (Ayer 1956, 94), since it
would be very difficult to pick a point in the continuous series of possible time intervals where
this change in accuracy occurs (Ayer 1956, 94). Therefore, regardless of the length of the time
interval, our senses are still an unreliable source of information about the world at the present
time and can never provide us with certainty in the truth of our beliefs.
In conclusion, we experience both illusions and hallucinations and we cannot tell whether
or not we are currently experiencing one of them. Also, we are only able to observe how objects
were in the past which may not accurately represent the present state of the objects. These
arguments show that our senses are an unreliable source of information about the world, and thus
cannot provide us with any certainty in the truth of our beliefs.
Bibliography
Crane, Tim, "The Problem of Perception", The Stanford Encyclopedia of Philosophy (Spring
2011 Edition), Edward N. Zalta (ed.), URL =
<http://plato.stanford.edu/archives/spr2011/entries/perception-problem/>.
J. Ayer, 'Perception' (extract) from The Problem of Knowledge, Harmondsworth: Penguin, 1956,
p. 87-94.
"Reliable." In Merriam-Webster. Last modified 2014. Accessed February 4, 2014.
<http://www.merriam-webster.com/dictionary/reliable>.
Rene Descartes, Meditations on First Philosophy [1641], ed. J. Cottingham, Cambridge:
Cambridge University Press, 1986, p. 13.
"Sense." In Merriam-Webster. Last modified 2014. Accessed February 4, 2014.
<http://www.merriam-webster.com/dictionary/sense>.
5