Whilst many philosophers were interested in science and its ability to discover
and evolve new ideas, not all of them shared the Rationalist’s approach to
knowledge. The Rationalist’s faith in necessity, reason and innate ideas was
attacked by Empiricist philosophers who believed that the main source of
knowledge was the senses.
The English philosopher John Locke (1632-1704) was
not alone in considering that the mind is “white paper,
void of all characters, without any ideas”. This idea can
be traced back to Aristotle, the pupil of the Greek
philosopher Plato, who said: “There is nothing in the
mind except what was first in the senses.”
The Main Empiricists
Apart from Locke, the other main philosophers who are
generally termed Empiricists are:
1. Bishop George Berkeley (1685-1783). An Irish philosopher and
clergyman, he is considered the founder of Idealism, a view which sees
ideas as the only reality.
2. David Hume (1711-1776). A Scottish philosopher and modern sceptic
who was to influence the twentieth century movement of Logical
Positivism (among others).
Though these three philosophers differed in the actual details of their
philosophies, they were all pretty much in agreement in their opposition to the
principles of Rationalism. We will now deal with these one by one.
Innate Ideas
The notion of innate ideas, as we have already seen, presupposes that certain
knowledge is present from birth. This is different to saying that some types of
knowledge are a priori (or true by definition). Empiricists would not want to deny,
for example, that “All bachelors are unmarried” is a truth independent of
experience. They would, however, deny that such a truth could be innate.
For the Empiricists, the mind is a Tabula Rasa (which is Latin for “blank slate”).
When we learn or experience things, it is as if the mind is being written on. For
the Rationalists, however, the mind is like a computer: the hardware already has
some functions (innate ideas) before the software (experiences, specific
knowledge) is loaded onto it.
If innate ideas don’t exist, is it possible to learn everything?
Simple ideas
The Empiricists want to argue that all our ideas come from experience. So, how
do we understand the world? Locke thought that our experiences provided us
with what he termed simple and complex ideas. Simple ideas might include the
redness of a rose, the smell of coffee, the taste of sugar or the sensation of heat.
We thereafter use these ideas as the basis for reflection, combining and
comparing them to form complex ideas in order to understand the world.
An example of this can be seen in the way we might get a better understanding
of heat. I might burn my hand on a flame, but also on an extremely cold piece of
ice. Reflecting on this and other examples I may come to the conclusion that it is
not heat which is solely responsible for burns, but difference in temperature (in
this case, the difference between my hand and the hot and cold things). Thus, the
simple sensations and experiences form the basis for more abstract ideas such as
Pick 3 things (they may be anything - objects, ideas, emotions, etc. – but try and
mix them) and list 3 simple ideas about them (I have done the first two as
examples). Do you reach a point were your simple ideas cannot be any simpler?
Object (Complex Idea)
Simple Ideas
A pen
Shiny, hard, small
The idea of beauty
Proportion, symmetry, pleasure
Primary and Secondary Qualities
If we reject, as the Empiricists do, the idea that all our knowledge comes from
rational principles, we are left with a major question: How can we tell which of
our perceptions are real or true? Locke’s answer is to suggest the existence of
what he calls primary and secondary qualities.
First of all, let us consider an object – a table, for example. Now, Locke’s view is
that certain qualities of the table are primary qualities of the object (such as the
table’s shape and size), but others - secondary qualities - are produced by
powers in the object itself, which act on our senses to produce sensations and
impressions. Such things as colour, taste and temperature are therefore
secondary whilst other primary qualities include number (how many objects there
are) and motion (an object’s speed or movement).
The main thing Locke was trying to do is to limit knowledge to the things that
could be said to be primary qualities. So, as far as the table is concerned, such
things as its size, shape and weight are fixed and measurable. Its colour, on the
other hand, is a matter of subjective opinion.
Of the simple ideas you listed in the previous example, which are primary and
which are secondary? Go through your lists and mark P or S next to each one.
Empirical Knowledge
Locke considered that knowledge could be of certain types depending on how
ideas could be compared. The idea of black, for instance, could be contrasted with
that of white; other ideas seem to share a common source, such as light and fire,
which quite often go together. These ways of building up information, Locke
thought, are the main means by which we turn simple ideas into complex ones.
But how certain is such knowledge? Locke considered that there are 3 main types
of knowledge:
1. Intuitive. This form of knowledge is the most certain because it seems
the most obvious to us and the most difficult to doubt. This would
include such things as “I have a body”, “Black is not white”, but also –
according to Locke – “God exists”. These, he argues, are so obvious
that we accept them intuitively. (This may also be called a priori
knowledge or truth by definition.)
2. Demonstrative. When we begin to put simple ideas together to form
complex ones, we are demonstrating something. So, for example, if I
compare the heat of the Sun with the heat of a fire, I may
demonstrate that they are both made of similar substances. (This form
of knowledge is less certain because it may change, therefore it is a
3. Sensitive. This form of knowledge is the most uncertain because it
relies merely on the evidence of the senses. If I look to see how many
chairs there are in another room, I am relying on sensitive knowledge,
which – as Descartes has shown – can, in some cases, be mistaken.
(This is also a posteriori, though the least certain.)
“Black is not white”
Most certain
“Sun is similar to fire”
Quite certain
“There are ten chairs”
Least certain
Locke’s idea of intuitive knowledge (that certain things seem intuitively to be
true) seems very similar to Descartes’ concept of clear and distinct ideas. Do
you think that Locke is any more successful in presenting an account of how
we may be certain?
Berkley and Idealism
Locke’s concept of primary and secondary
qualities, whilst intended to help us make
sense of the limits of knowledge, also had an
unintended use. Locke had argued that some
of the information which we receive through
our senses is subjective and should not be
trusted (secondary qualities), whilst other
information could be considered objective and
From Locke’s point of view, the thing that
possessed these different qualities – the
substance – could never really be known in
itself. If, for example, we consider once again
the example of the table, we can be aware of
such things as its colour or texture (secondary
qualities) or its shape and size (primary
qualities). But we cannot know the thing itself
because everything we experience about the
table will come under one of these two categories.
The Irish philosopher George Berkeley (1685-1783), pointed out that if all we
ever see are primary or secondary qualities, how do we know that substance
really exists? In other words, there may be no such thing as matter. This view
is called Idealism.
Berkeley’s Criticism of Locke
Berkeley considered Locke and other philosophers to have opened the door to
atheism and scepticism by this view of knowledge. In an attempt to defend
faith in God and knowledge from such attacks, Berkeley attempted to show
that, rather than sensations of objects arising from powers in the object itself
(as Locke thought), the experiences were actually in the perceiver (us).
What this means is that the object does not need to possess any powers with
which it produces effects on our senses, because the object does not exist
apart from our perception of it. This allows Berkeley to deny the sceptical
argument that we do not see objects as they really are.
Berkeley’s View of Reality
Arguments for Idealism
The main arguments for Idealism are based on the idea that our perceptions
of objects are in us. In other words, when we say that an object is red its
redness is part of our perception of it, not in the object or - as Locke argues an effect of some power of redness in the object.
So what arguments does Berkeley use? First he attacks the idea that
secondary qualities can exist in the object:
1. Sensation. When you put your hand in cold water, the temperature
feels different depending on the temperature of your hand. If your
hand is hot, the water will feel colder; if your hand is cold, the water
will feel warmer. The water cannot be hot and cold at the same time.
Therefore the perception of temperature must be in the perceiver.
2. Taste. If a taste is pleasurable, such as the sweetness of sugar, how
can we say that pleasure exists in the object itself (the sugar)? This
would be to ascribe feeling to an inanimate substance - which would be
ridiculous. Therefore, since we cannot separate the taste of sweetness
from our pleasure, both must exist in the perceiver and not in the
object (the same obviously goes for displeasure).
Next he tries to show that some perceptions are relative, attacking both
primary and secondary qualities:
3. Colour. If two people see the same object from different perspectives,
one might think it was a different colour to the other. Both colours
cannot exist in the object at the same time, so the colour must exist in
the perceiver and not in the object.
4. Speed. If I am standing still and I see a train passing, the people on
that train are moving at a certain speed, but to each other they appear
to be sitting still. If speed exists in the object, how can the people on
the train be both moving and at rest? The answer must be that the
quality exists in the perceiver.
Finally, Berkeley tries to show that there is no difference between real and
apparent qualities:
5. The Master Argument. Berkeley's main argument is meant to show that
it is impossible for something to exist without being perceived (or, as he
says, esse est percipi, Latin for "To be is to be perceived"). This means
that if we cannot imagine what the perception of something must be
like, we cannot really say that it exists. Berkeley uses this idea to attack
the notion of substance or matter, for if all the qualities that we ascribe
to it are either primary or secondary qualities, can we actually say that
the substance itself exists?
Think about what problems there might be with this. Briefly outline:
1. What might this view mean for science?
2. How it might be possible to verify our perceptions?
3. Is it possible to prove or disprove Berkeley’s argument?
The Scottish Philosopher David Hume (1711-76) is
widely known for his sceptical attitudes to certain
types of knowledge. As with the other Empiricists,
Hume disagreed with such philosophers as
Descartes that the mind contained innate ideas. He
also criticised the idea that we could be certain
about anything outside of our experience or the true
nature of the world.
Hume’s Fork
Hume divided knowledge into what he termed
“relations of ideas” and “matters of fact”. Relations
of ideas are what we have been calling analytic
truths or a priori knowledge. These are such things
as “All bachelors are unmarried”, “2 + 2 = 4”, etc. These are certain in as much
as we cannot conceive of them being otherwise. Matters of fact, however, can be
falsified. I may say, “The sun will rise tomorrow” (which is extremely likely) – but
is not impossible that it will not.
Ideas and Impressions
For Hume, ideas are simply weaker versions of sense impressions. So, for
instance, an idea of the Sun is not as vivid as actually looking at the thing itself.
Furthermore, nothing can exist in the mind without either first being experienced
or formed through the combination of other experiences.
How might Hume account for the following ideas?
1. A mermaid
2. A golden mountain
3. Heaven
The Rationalists argued that there was such a thing as “necessary connection”.
We looked at the idea of necessity earlier and saw how it was meant to show that
certain things were the case because mathematical or logical principles meant
that they could not be otherwise.
However, Hume argued that all our knowledge of cause and effect came through
habit. So, for instance, if we see the Sun rise it is not because it corresponds to
some eternal and unchangeable law, but because we have seen it rise countless
times – what he terms, “constant conjunction”. Therefore, the more we have
experienced things, the more certain they will be.
For Hume, cause and effect is nothing more than habitual perception. Are there
any examples that might contradict this? Also, Hume sees miracles as being
unlikely for this exact reason – that they have not been observed often enough.
Can this view be criticised?
Sense Data and Scepticism
In unit 2, we saw that rationalists attempt to overcome sceptical arguments by
appeal to first principles. So, for instance, Descartes attempted to prove the
reliability of the senses (within limits) and the existence of the outside world by
appeal to the idea that God exists, was not a deceiver and that therefore certain
things could be clearly and distinctly perceived.
However, empiricists deny these first principles, arguing instead that such ideas
are either true by definition (all bachelors are unmarried) – and therefore tell us
nothing about the world – or are built up from experience. This seems to leave
the empiricism more open to sceptical attack as there seems to be no way of
guaranteeing the truth of individual perceptions. At least with rationalism there
was an attempt to give certain knowledge a different origin than that of sense
experience. However, since empiricists argue that all knowledge ultimately comes
through the senses, there seems to be a greater possibility of deception. In fact,
the only form of absolute knowledge that they are left with are truths by
definition – which tell us nothing about the world anyway.
In the end, what the empiricist is left with is just “sense data”. In other words,
whilst we cannot be certain that a chair in front of us actually exists or
corresponds to our idea of it, we can at least be certain that we have a certain
sense impression. “Sense data” is therefore a term for everything that we
perceive (philosophers have also used other terms – such as “percepts”, “ideas”
and “impressions”).
In the last two units we have looked at the different approaches to knowledge
and the various arguments involved in attempting to guarantee knowledge. Most
of the philosophers we have looked at have tried to argue that either reason or
experience is responsible for knowledge and are therefore termed either
"Rationalists" or "Empiricists". In the next unit we will look in more detail at
exactly what role perception plays in knowledge. To test your understanding so
far, you will finish this unit by completing the essay assignment below.
Answer the following past paper question below (answer all parts). The deadline
for submission is October 9th 2002. Essays may be handwritten or typed.
Submissions may be via email, post or in person. There is an upper word limit of
2000 words, and a lower limit of 600.
1. Answer each part individually (total marks = 45) :
a) Explain and briefly illustrate the meaning of a priori and a posteriori
knowledge. (6 marks)
b) Identify and explain two reasons why empiricism may lead to scepticism
concerning the extent of our knowledge. (15 marks)
c) Assess the view that all our concepts are derived from sense experience. (24