John Locke is really a very clear and sensible
writer, as you would soon see yourself if you had the time to go look
at his Essay Concerning Human Understanding or any other of
his philosophical writings. But the Essay is also very lengthy,
so I've not assigned you to read any of it this quarter. Instead, I'm
going to just tell you a few of the main points he makes in that book.
So after some introductory words, the following mini-lecture will be
divided into eight of the key points Locke would most like you to learn
from his book.
In his youth Locke seriously intended to
enter the seminary to become a priest, but in the end he chose to study
medicine instead. He became a physician, but practiced only a little,
devoting most of his time to writing and official duties.
Locke considers epistemology to be "first
philosophy," because he considers it to be the discipline that
examines the instrument that does the knowing and philosophizing, viz.,
the human mind. When you take a biology course, your first lab will
be to study and understand the microscope, because the microscope is
such a crucial instrument in learning about biology. In a similar way,
philosophy's first task should be to examine how the human mind knows
anything, which is the task of epistemology. And the first task of
epistemology should be to find out if the mind is even capable of knowing
anything, and if it is, what are the limits to what it can know.
In his epistemological studies, as we will
see below, Locke relies much more heavily on direct sensory experience
than on logic and reason. He believes direct experience to be a more
reliable source of knowledge than logic and reason. Descartes, a philosopher
in the rationalist tradition, chose to rely more on reason and logic
for his analyses, but Locke is, after all, a physician. Physicians
rely on evidence they get from their patients, they form hypotheses
as to what might be the underlying problem with their patient, and
they attempt treatments. If the treatments don't work they form another
hypothesis and attempt another treatment, and so on. Absolute certitude
may be something mathematicians can hope for, but the physician must
rely on experience and testing. Locke believes that is also how we
derive our knowledge about the world.
In any case, following are some of the key
points to learn from Locke's Essay.
I. There are no innate ideas
Locke spends the entirety of Book I in his Essay arguing
that human beings have no inborn, or innate, ideas in their minds at
birth. Some of the rationalist philosophers wanted to claim that when
a human mind comes into the world it already understands such fundamental
principles as the principle of non-contradiction - that a thing cannot
both be and not be at the same time in the same respect - and the principle
that the whole is more than the part. Locke does not believe that we
are born with any of these inborn ideas.
Locke believes that when a human mind is
first born - whether the birth of that human mind be dated at the moment
of parturition (birth), or earlier at the moment of conception, or
at some point in between - when the human mind first comes into existence
it does not come with any inborn ideas. When it first exists it is
a blank slate, a "tabula rasa," an empty surface on which
experience will then subsequently write all that we ever know. We may
be born with automatic instinctual behaviors - such as automatic reflex
motions in response to some stimulus - but these are not ideas or perceptions
or what today we might call "contents of consciousness."
II. All ideas come from
All contents of consciousness, that is, everything
that ever gets into the mind, comes into it from one source only, and
that source is experience. Experience is the one source of input into
the human mind.
There are two kinds of experience, for Locke.
a. Experience of the outer world, which he
terms sensation, and from this mode of experience we derive
such notions as blue, round, solid, smooth, heavy, large, etc.
b. Experience of the inner world, which Locke
terms reflection, and from this mode we get such notions as fear, love,
willing, doubting, affirming, thinking, feeling, believing, remembering,
planning, anticipating, and so on.
For Locke, the term "idea" is rather
a technical term. By "idea" he means anything that
exists in consciousness, i.e., anything that exists in the mind.
So to sum up these first two points, no ideas
are inborn in the mind; instead, all ideas, that is, all contents of
the mind, come to us ultimately from only one source, experience (either
sensation or reflection).
III. Simple and complex
There are basically two sorts of ideas, simple
and complex. Simple ideas include all our simple sensory sensations
such as red, cold, sweet, loud, soft, round, etc.
Complex ideas are complexes of simple ideas.
For example, my sensory experience of a red ball would include a mixture
of the simple ideas of red, round, hard, cool, etc. That complex of
simple sensations goes into making up my experience of the ball. That
is to say, the sensation of this red ball that is in my mind right
now, i.e., the "idea" of the ball, derives from the sensory
experience of the ball that I am presently experiencing.
In all his thinking about how knowing works,
Locke sees himself as following a very common sense way of thinking.
He does not see himself as saying anything particularly abstruse or
unusual, and certainly not as saying anything that every common sense
person wouldn't agree with. In this next section, though, at least
toward the end of it, based on common sense though it is, we might
at first think he is saying something that common sense should not
accept. But you might want to reserve your judgment on that for a while.
IV. Ideas are caused in
us by qualities
sensations) in minds are caused by qualities in things. For
example, the sensation (or idea) of red in my mind is caused by the
quality of red in the thing.
So we now need a definition of what a quality
is. Here it is: A quality is a power in a thing to cause an
idea in a mind. So a quality is not a thing, really, but is a power in
a thing to cause an idea in a mind.
Now this is where it gets interesting. There
are two kinds of qualities, according to Locke, primary and secondary.
(He actually says there are three kinds of qualities, but we're going
to ignore the third kind for now.)
Primary qualities are those that every physical
object, every body, must have. Primary qualities are actually in the
physical object. There are only six primary qualities:
Every physical object, in order to even be
a physical object, must (according to Locke) have solidity, must have
some shape and size, must be either in motion or at rest, must be either
one or many, and must have some texture.
Secondary qualities, on the other hand, are
nothing but powers in things to produce a sensation in a mind.
Now this is an idea that we will need to explore in a bit more detail.
Let's consider the old philosophical question:
When a tree falls in the forest and there is no one around to hear
it (i.e., no ears of any sort, no squirrels, reindeer, frogs, lemurs
or pachyderms), does it make a sound?
Locke's answer would be this. A sound is
a sensation in a mind. So "sound" is the kind of existent
that exists inside minds, not out in forests. Now the sensation of
sound in a mind is caused by a quality out in the world, so
let's examine what quality is out there in the world that would cause
that sound sensation in your mind.
When a tree falls, it is passing through
a medium (air), and in the process of passing through that medium,
it causes impact waves in that medium. See the illustration below.
(note: No graphic artists were
harmed or mistreated in the production of this image, and the illustration
is definitely not drawn to scale.)
Here's what's happening: In the act of falling,
the tree passes through a medium (air), and in the process sets up
impact waves which move through that medium (much like dropping a pebble
in a pool of water causes waves to ripple outward in the medium of
water). The impact waves are not themselves sound, but if they strike
an auditory apparatus of some sort (like an eardrum-auditory nerve-brain
combination) then those waves can cause the sensation of sound ("Boom
and Crash") in those brains. So the sound is clearly inside the
brain, and what is outside in the world is a quality that has
the power to cause a sensation of sound in a brain.
So if there are no brains or hearing apparatuses
around, then there are no sounds. In fact, if a tree falls in the forest
and there are people there, there is still no sound in the
forest. The sound is always in the sensorium of the experiencing
brain, not out there in the world. What is out there in the
world are impact waves in a medium. Those waves are not themselves
sound, but they can cause sound if they impact a hearing apparatus
(like the ones for squirrels, lemurs, pachyderms humans, and others).
So sound is never "out there," no
matter what sound we're talking about. It is always in a mind. What
is out there is some sort of quality which has the power to
cause a sensation in a mind.
What Locke would have us notice here is how
completely different the impact waves out there in the world are from
the sound sensation that exists in a mind. These two realities are
totally different kinds of entities. Impact waves are out there moving
through air. Sound is a sensation that happens in a mind. Very different
kinds of realities.
The concept of the transducer might help
us here. Locke did not have transducers around when he was writing,
but if he had, he would have loved the idea. A transducer is something
in the world of electronics. A transducer is basically any electrical
device that changes, or transduces, one form of energy into another
form of energy.
A lightbulb, for example, is a transducer.
It changes simple electricity (which is not visible) into visible light.
It is important to notice here that what goes into the lightbulb (electricity)
is not at all the same thing that comes out of it (light). A very naïve
person who saw an electric cord leading into the lightbulb might wrongly
guess that the cord carried light into the lightbulb. That would be
naïve and wrong, of course. In much the same way, what is impacting
onto our hearing apparatus is a series of moving waves in a medium.
The impact of those waves on our eardrum, and then on into the inner
ear, the auditory nerve, and so on, then transduces all that
input into a sound. And what Locke would have us notice is that a sound
sensation is a very different kind of animal than an impact wave in
A radio receiver is another example of a
transducer. It takes radio-frequency (RF) waves passing through space
and transduces them into something we can hear. The RF waves are not
themselves hearable until they have been transduced by the receiver.
Our visual apparatus is also a kind of transducer.
Light waves come streaming into our eye and impact on the surface of
the retina. From that point on our visual apparatus (retina, rods & cones,
optical nerve, brain, etc) transduces those light waves into a sensory
experience with color, shape, size, etc.
Now we sometimes assume that when any two
of us look toward the same object, we must each also be having the
same sensory experience. That is, we assume that we each transduce
those light waves into the same visual experience. We might even assume
that if my dog and I look toward the same object that we will both
see the same thing. Or that a lizard and I would see the same thing.
But the fact is that different organisms, i.e., different visual apparatuses,
in fact transduce things quite differently than humans do.
Many years ago I saw a nice layout in a magazine
(unfortunately this was so many years ago - I think I was still in
college - that I no longer recall the magazine or date) which showed
an array of photographs taken of a single daisy. The interesting thing
was that each photograph was taken through the visual apparatus of
a different animal. I believe the photographer may have been Lennart
Nilsson, or at least was a photographer who used lasers in his photography,
and the photographer was able to somehow get the camera to "see" the
daisy through the visual apparatus of several different animals. There
was a photo of the daisy as seen through the eye of a dog, a lizard,
a housefly, and so on. What was interesting was how astonishingly different
the daisy appeared through the visual apparatus of those different
organisms. In some it was colored certain ways, in others it was colored
other ways, in some it was shades of gray with no other colors, in
some the shape appeared nothing like a daisy, in some the image was
multiplied, and so on. In some cases it appeared so different as to
not even be recognizable as a daisy.
It was actually a two-page layout, with these
dozen or so images laid out on the left side of the display. Then on
the right side of the display was a full page photo of the daisy as
seen through the human visual apparatus. The implication of the layout
seemed to be, since the photo of the daisy as seen by a human was so
much larger, that "This is the way the daisy truly appears,
viz., the way it is seen by humans." But of course that implication
would not be accurate. The photo of the daisy as seen through the human
eyes should have been no larger than the photos through the eyes of
all the other organisms.
In any case, that photo layout really brought
home to me that we all transduce the stimuli that come into us so that
it will register in our brain in categories that our brain is designed
to understand. And that every other organism does the same thing.
Now let's bring this back to John Locke and
his notion of secondary qualities. This notion that our brains transduce
the stimuli that come into them is exactly what Locke meant when he
said that secondary qualities are nothing but powers in a thing
to produce sensations in a mind.
So Locke's notion is that everything we perceive
besides the six primary qualities (solidity, size, shape, texture,
number, and motion/rest) are all secondary qualities. They aren't really
out there in the world in the way we think they are. Sound isn't really
out there in the world in the way we think it is. Nor is color. Nor
is temperature, taste, smell, and so on. Neither are other sensations,
like pain, for example. We all realize that the pain we experience
is not actually out there in the world. We realize that pain is a sensation
we have in our brain/mind and that it is caused by something out there
in the world (a needle, a burn, etc) which is not itself pain. It is
just the cause of pain. We know the same thing about the sensation
of tickle, that it is not out there in the world. There may be a feather
out there in the world that some cruel person is maliciously applying
to us, but we realize that the tickle is purely a sensation that exists
in our mind (or brain). Well, Locke just wants us to realize that all
our other sensations (except the six primary qualities) are also just
in our minds.
V. Judgment constantly alters
This fifth point is simply that there is
a crucial difference between "sensation" and "perception" (to
put this in contemporary terms). Sensation is simply the raw data that
your senses bring into your brain, and perception includes the judgments
and interpretations that you add to the sensations so that it ends
up having some meaning for you.
Perhaps an example will make this clear.
I once went with a friend to the Chicago
Art Institute and on the second floor was an enormous painting which
took up one entire wall. It reached clear up to the ceiling and all
the way down to the floor. It was an amazingly realistic and full-size
painting of a hallway in an art museum, so as you stood looking at
it, you had the impression you were looking down a hallway which then
opened into another room of the art gallery. You could see some paintings
hanging on the wall in the hallway, and one or two people standing
looking at them. It was all very realistic, and since it took up an
entire wall, with no noticeable frame around it, you could easily believe
that you were looking at an actual hallway.
Well, the Art Institute had to put a big
piece of plexiglas up in front of this painting because people kept
walking into it and bumping it.
The people who walked into the painting were
having certain raw sensations when they saw the large painting (simple
two-dimensional shapes of various sizes, etc on a flat wall), and to
those raw two-dimensional sensations they added certain non-conscious
judgments and interpretations about what those shapes and sizes meant.
They thus interpreted the two-dimensional shapes to have three-dimensional
meanings. They interpreted the lines and colors they saw on the wall
to mean that there was open space in front of them.
According to Locke (and to most contemporary
sensory psychology too), we do this all the time in all our perceptions.
We receive only the raw sensation, but we always overlay that raw sensation
with our non-conscious judgments and interpretations, and then what
result from that are our perceptions. So the formula would look like
sensation + judgment = perception
Or raw sensation, plus how we construe those
sensations, yields what our minds then perceive.
VI. Naive realism vs critical
Locke's next point is the distinction between
naïve realism and critical realism.
First, though, we must distinguish between
the philosophy of realism and the philosophy of idealism. Realism is
any philosophy which holds that there is a real world out there, and
that our sensations and perceptions result from an encounter with that
real world. Idealism (as you would seen in George Berkeley if you read
him) is any philosophy which holds that there is no real world out
there, and that the only things that exist are our perceptions and
Locke is definitely a realist. He believes
that there is a real world out there, and he believes that's what good
common sense teaches us too. But Locke wants to distinguish between
a naïve realism and a critical realism. Naïve realism would
be the unreflective belief that there is a real world out there, and
that our perceptions are an exact copy, an exact replica, of what is
actually out there in the world. Naïve realism thinks of our senses
as more or less like a simple brownie camera, in which we open our
senses to the world and the world comes simply streaming into our mind
and leaves a perfect copy of itself in our perceptions. Naïve
realism would not be aware of how much our senses and brain transduce
the information that comes into them.
Locke considers himself to be a critical
realist. Critical realism is the belief that yes, there is a real world
out there, but our sensations and perceptions are not simple copies
of that real world. Critical realism believes that our senses really
do transduce and modify the incoming data so that it will register
in our minds in ways that make sense to our brains and minds.
Perhaps a metaphor can help this more understandable.
Suppose a classroom full of little laptop
binary computers all sitting in a circle and having a discussion amongst
themselves. All any of them can perceive, of course, are ones and zeros,
since they are all binary computers and that is all that binary computers
can perceive. (If we want to communicate with our computers, you know
that we must translate everything we want to say to them into ones
and zeros; so if I want to say "L" to my computer, I have
to translate that L into 10001010 so that the computer can understand
it, because strings of ones and zeros are all that its little processor
In any case, imagine all these little computers
thinking about what the real world out there must actually be like.
The naïve realists among them would believe that the world consists
of nothing but ones and zeros, because that is exactly what they all
see. The critical realists among them would believe that yes, there
must be a real world out there, but it probably does not consist of
only ones and zeros. "The world comes streaming into us through
our input devices," says one critical realist computer," but
our input devices transduce the world into the categories that we can
understand, which is ones and zeros. The world out there is not actually
ones and zeros, but ones and zeros are the only categories we have
for perceiving the world, so if we're going to see anything at all,
it will have to register with us in those categories."
Locke believes that we are just like the
binary computers, except that we have a few more categories of perception
than they do. (Later we will see that Immanuel Kant believes that we
have twelve or fourteen categories of perception.)
To sum up, naive realism believes there is
an isomorphic relationship between what we perceive and what is actually
out there in the world. You don't have to learn much sensory psychology,
though, before you discover that Locke's critical realism is probably
a lot closer to the mark
VII. Four kinds of existents
Locke believes that there are only four kinds
of realities (existents) that exist in the world.
1. He believes there are selves (or
minds). He believes that we know about the existence of minds
both our own and those of other people -- by a process he terms "intuiting."
2. The second kind of existent Locke calls ideas,
i.e., the contents of minds. He believes we know about the existence
of ideas by reflection.
3. The third kind of existent is things, or physical objects. Locke
believes that we know about the existence of things through sensation.
4. Fourthly, Locke believes that there is a God, and that we know
about God's existence by logical proofs for his existence. (We will not
be looking at any of the classical arguments for the existence of God,
but if you ever take a Philosophy of Religion course you will learn about
VIII. Two big questions
Finally, there are two key questions Locke
considers it important to ask, and it may even be that the asking of
these two questions is more important than the specific answers Locke
gives to them.
first question is this: Can we know that things continue to exist
during the intervals that they are not being observed by anyone?
For example, imagine that you are perceiving the mug on your desk,
but that you then turn away from it so that you are no longer perceiving
it in any way (and neither is anyone else). You do not see it, feel
it, hear it, smell it, or perceive it in any way (and neither does
anyone else). Then you turn back and perceive it again. Then you
turn away and are no longer perceiving it. The question is this:
during the intervals that the mug is not being perceived, can we
know that it continues to exist during those intervals?
This may seem like a silly question, but
when one is doing epistemology it is important to examine closely
the assumptions that are made about what it is possible to know.
And Locke is willing to examine this assumption we all seem to have,
that things somehow continue in existence even though no one is perceiving
them. So that's question number one.
second question is this: Even during the times that we are directly
observing an object can we know for sure that the object actually
Now the answers that Locke himself proposed
for these questions are not nearly as important as the fact that he
posed the questions. The next two philosophers who follow Locke in
the empiricist tradition - George Berkeley and David Hume - take these
two questions very seriously and suggest answers very different from
those that Locke offered.
Just for the record, though it is not particularly
important for our purposes here, here are the answers that Locke proposed
for these two questions.
we know that objects continue to exist even when they are not being
perceived by anyone? Answer: Well, perhaps we cannot be absolutely
certain of their continued existence during the times when they are
not being perceived, but common sense tells us that in all probability they
do continue to exist even when not being perceived.
can we know that objects exist even when they are being perceived?
Locke's answer: Surely no one would be so skeptical as to hold that
we cannot know objects exist when they are being directly perceived.
Common sense tells us that of course we can know that objects exist
during the intervals that we are directly perceiving them.
You might now ask yourself whether you think
Locke's answers to these two questions should be considered adequate
George Berkeley, while he greatly admired
Locke and his work, did not consider that Locke had carried his
epistemological examinations quite far enough. I sometimes wonder
if Berkeley may have thought that Locke lost a bit of his question-asking
courage here when he caved in to too-simple answers to these two
So one of the big questions Berkeley takes
up when he writes both his Principles
of Human Knowledge and his Three
Dialogues Between Hylas and Philonous is the even more central
question: What does "to exist" actually mean? We may assume
that we understand this simple word which we use so easily and frequently,
but what exactly are we claiming when we claim that a thing "exists?"
Berkeley's answer to this question is a most