John
Locke’s Theory of Knowledge
(An Essay Concerning Human Understanding) John Locke’s epistemology by Casper Hewitt
Published
in 1690, An Essay Concerning Human Understanding is
the masterwork of the great philosopher of freedom John Locke.
Nearly twenty years in preparation Locke began working on The
Essay in 1670 following a series of philosophical
discussion during which he and his friends decided that “it was
necessary to examine our own abilities, and see what objects our
understandings were, or were not, fitted to deal with.”
The Essay is an attempt to establish what it is
and isn’t possible for us to know and understand. “My
purpose” Locke says, is “to enquire into the origin,
certainty, and extent of human knowledge; together, with the
grounds and degrees of belief, opinion, and assent.” The aim
thus is not to achieve certainty, but to understand how much
weight we can assign to different types of knowledge.
The Essay is
divided into four books, the first three laying the foundation
for the arguments set out in Book IV. Central to Locke’s
argument throughout the Essay is the idea that
when we are born the mind is like a blank piece of paper. He
says:
Let
us then suppose the mind to be, as we say, white paper void of
all characters, without any ideas; how comes it to be furnished?
Whence comes it by that vast store, which the busy and boundless
fancy of man has painted on it, with an almost endless variety?
Whence has it all the materials of reason and knowledge? To this
I answer, in one word, from experience: in that, all
our knowledge is founded; and from that it ultimately derives
itself.
What
Locke is talking about here is the content of
the mind, not its abilities. It is important to highlight this as
the notion of the mind as white paper (or as a blank slate to use
another popular metaphor) is one that is still contentious today
and different people mean different things by it. Locke clearly
believes that we are born with a variety of faculties that enable
us to receive and process information (the senses, memory, our
ability to use language, explored in some detail in Book III of
the Essay) and to manipulate it once we have it, but
what we don’t have is innate knowledge or ideas.
Book
I of the Essay, Of Innate Notions is
dedicated to refuting the hypothesis that we are born with
imprinted or innate ideas and knowledge, something that puts him
at odds with the thought of Descartes. But it is not just
Descartes that he is refuting here. At the time it was widely
thought that certain ideas and principles were imprinted on human
beings from birth and that these were essential to the stability
of religion and morality and I think this is one reason why Locke
spends so much time debunking the notion of innateness. But there
is much more to it than that. Locke believed deeply in humanity.
He was not a secular thinker, in fact he was a devout believer in
God, but he thought that the God-given faculties we possess,
especially the ability to reason, gave us a unique place in
nature which we should take full advantage of. Locke was a
political animal, intimately involved in the changes taking place
in England at the time, and a great believer in individual
freedom. His was a political project and his interest in the mind
had a practical purpose behind it – he wanted to transform
society and organise it in a rational way. His rejection of
innate ideas was intimately linked to this project for it is all
too easy to claim all sorts of principles as innate in order to
maintain the status quo, meaning that people “might be more
easily governed by, and made useful to some sort of men, who has
the skill and office to principle and guide them. Nor is it a
small power, it gives one man over another, to have the authority
to be the dictator of principles, and teacher of unquestionable
truths; and to make a man swallow that for an innate principle,
which may serve his purpose, who teacheth them.”
Let’s
examine his argument. Consider for example the simple notion that
it is not possible for something to both exist and not exist.
Locke argues that if such a proposition were innate then every
person in every period of history would know and understand this,
but this is clearly not the case. If such truths were ‘imprinted’
on us all then we would expect that “childrenand idiots”
would not only be fully aware of them, but also be able to
articulate them. For Locke it makes no sense to imagine both that
ideas or knowledge are innate and that we do not know them, thus
in his own words: “It seems to me a near contradiction to say
that there are truths imprinted on the soul, which it perceives
or understands not; imprinting if it signify anything, being
nothing else but the making certain truths to be perceived.” He
goes on to take up the suggestion that innate propositions are
only perceived under certain circumstances. The crux of his
argument is that once we start to think in this way it becomes
unclear what is meant by innate ideas at all – if we are not
all aware of them nor able to perceive them can they really be
described as innate? Accepting such a view would make it
impossible to distinguish between innate ideas and new ideas that
we discover.
He
also takes up at some length the claim that innate propositions
are discovered when people come to use reason. For Locke it makes
no sense to describe a truth that is discovered through the use
of reason as innate and he constructs a careful argument to back
this up, investigating and refuting different interpretations of
the claim. I do not have space here to go into too much detail
here, but Locke goes on to reject the claim that there are innate
practical moral principles or that we are born with innate ideas
of God, identity or impossibility.
Book
II of the Essay, Of Ideas, lays out how
human beings acquire knowledge, beginning by making a clear
distinction between different types of ideas. There are simple
ideas which we construct directly from our experience and complex
ideas which are formed by putting simple (and complex) ideas
together. Locke divides complex ideas into three types which he
describes as ideas of modes, substances and relations. Modes are
“dependences on, or affectations of substances” and
relations. Thus they are things that depend on us for their
existence, including things as diverse as the ideas of gratitude,
rectangle, parent, murder, religion and politics. Substances are
things in the material world that exist independently, including
what we would generally describe as substances such as lead and
water, but also including beings such as God, humans, animals and
plants and collective ideas of several substances such as an army
of men or flock of sheep. Relations are ideas
that consist “in the consideration and comparing one idea with
another.”
Locke
proposes that the mind puts ideas together in three different
ways. The first is to combine simple ideas to form complex ones.
The second is to bring two or more ideas together and form a view
of them in relation to each other. The third is to generate
general ideas by abstracting from specific examples. Thus we
ignore the specific circumstances in which we gain a particular
piece of knowledge, which would limit its applicability, and
generalise so that we have some rule or idea that applies in
circumstances beyond our direct experience. This interpolation
and abstraction is important in a number of areas (morality for
example) but is of course essential to science, and Locke’s
familiarity with the mechanical philosophy provided part of the
reason for emphasising this way in which we generate ideas. He
goes on to discuss how sensation and reflection give rise to a
number of kinds of ideas, including moral relations and ideas of
space, time, numbers, solidity, identity and power.
By
far the longest chapter in Book II is a discussion of power and
this is particularly interesting in that it provides an
opportunity to explore the notions of free will and human agency,
which lie at the heart of Locke’s political project. Here we
are not talking about power in the sense it is used in physics
(the rate at which energy is used) nor about the power one person
exerts over another, but rather in a much more general sense of
an ability to make a change (active power) or receive a change
(passive power). For example “fire has a power to
melt gold … and gold has a power to be melted
… the Sun has power to blanch wax, and wax has
a power to be blanched by the Sun.” Thus “the
power we consider, is in reference to the change in perceivable
ideas.”
Locke’s
primary interest in power is, unsurprisingly, not related to
substances in general, but is in the abilities of human beings,
in particular the powers or faculties of the mind such
as liberty, will and desire.
He defines liberty as “a power to act or not
to act, according as the mind directs” whereas the will is
a “power to direct the operative faculties to motion or rest in
particular instances,” and argues that desire is
an uneasiness “fixed on some absent good, either negative, as
indolency to one in pain; or positive, as enjoyment of pleasure.”
He is careful to distinguish between these powers and the person
(theagent) who possesses them, for these faculties are not
“real beings in the soul” that can perform actions – only
the person acts. In a similar vein he argues that one power
cannot operate on another, “it is the mind that operates, and
exerts these powers; it is the man that does the action, it is
the agent that has the power, or is able to do.”
Thus
for Locke the idea of free will is nonsensical –
a person can be free “to think, or not to
think; to move, or not to move, according to the preference or
direction of his own mind,” but the will cannot,
for it is simply one of the faculties of a person – the will
does not think, nor can it choose a course of action, thus how
can it be free? In order to emphasise the distinct nature of the
powers discussed he points out that “there may be thought,
there may be will, there may be volition, where there is
noliberty.” For example a man falling into water from a
height “has not herein liberty, is not a free agent” since,
although he would prefer not to fall he is not in a position to
act on that preference. Similarly a man hitting a friend due to a
convulsive movement of his arm would not be considered by anyone
to have liberty in this as it is out of his control – he has no
choice in the action.
Locke’s
discussion of identity is also interesting in that it explores
what we mean when we think of something retaining a particular
identity. If we are dealing with an inanimate object this is
quite straightforward, we simply have to ask whether it consists
of the same matter, but if we are considering a living being
things are not so straightforward: “a colt grown up to a horse
… is all the while the same … though there may be a manifest
change of the parts.” Here identity is associated with some
continuity of life of the being in question rather than it
consisting of the same matter. When it comes to humanity the
question of identity becomes further complicated and Locke makes
an important distinction between a human being (‘man’) and a
‘person’. The identity of a human being is the same as that
of any other animal, defined by “participation of the same
continued life,” but a person is “a thinking
intelligent being, that has reason, and reflection, and can
consider itself as itself, the same thinking thing in different
times and places.”
Book
III of the Essay, Of Words, is central to
Locke’s epistemology or theory of knowledge. He explores the
intimate connection between the names we give to things and ideas
and, following the arguments detailed in Book II, links language
and ideas directly, claiming that most words “are names of
ideas in the mind.” He does deal with other types of word, such
as particles that “signify the connexion that the mind gives to
ideas, or propositions, one with the other” but his focus is on
words that represent ideas in the mind. Thus most words can be
classified according to the same categories as ideas were in Book
II; words for substances, modes and relations.
He
emphasises that when we use words they always represent the ideas
the person speaking has in his or her head, which are not
necessarily the same as the ideas associated with those words in
the mind of the person listening. However, language is such that
people generally assume they mean the same thing when they use a
particular word and, further, “often suppose their words to
stand also for the reality of things.” This leads him to
explore different types of words, how we understand them, and how
we use them to increase knowledge. He points out that most words
are general terms arguing that if this weren’t the case
language wouldn’t be much use for improving knowledge, for
while knowledge is “founded in particular things” it
“enlarges itself by general views.” He sees words as becoming
general “by being made the signs of general ideas” and it is
here that the intimate connection between words and ideas is key.
Locke
claims that it is not possible to define the names of simple
ideas, only complex ones, since simple ideas are rooted in the
things that we sense and can only be named by reference to the
things themselves: “Simple ideas … are only to be got by …
impressions, objects themselves make on our minds.” He cites
the problem of trying to define the meaning of the word light to
a blind man as an example. Without the sense of sight it is not
possible to understand any definition put forward in the way a
sighted person can. Complex ideas, on the other hand, can be
defined in terms of simple ideas, provided we are equipped with
all the appropriate senses (e.g. sight) for understanding the
simple ideas used. For example a rainbow can be defined in terms
of its shape, the colours it consists of and the order they
appear in.
Pointing
to the non-universal nature of words and language, Locke points
out that words in one language do not always have an equivalent
in another “which plainly shows, that those of one country, by
their custom and manner of life, have found occasion to make
several complex ideas, and give names to them, which others never
collected into specific ideas.”
Locke
also discusses the essence of a sort or species
of idea, by which he means “that abstract idea to which
the name is annexed; so that everything contained in that
idea, is essential to that sort.” He makes a distinction
between the nominal andreal essence of
a sort. The nominal essence is the complex idea a word stands
for, while the real essence is the true properties or
constitution of the thing we describe by the word, some of which
we may know, but many of which we usually don’t. This
distinction is extremely important to Locke’s overall thesis
since the aim of the Essay is to examine what we
can and cannot know. For Locke the real essence of something is
not something we can ever know, as there will always be some
properties, or some behaviour that we are unaware of. Nominal
essences on the other hand will vary from person to person. For
example the “yellow shining colour, makes gold to
children; others add weight, malleableness, and fusibility; and
others yet other qualities …” However, we have to be very
careful when we talk of real essences. For one thing we only
suppose their being, without knowing what they are, but also the
real essence of a substance such as gold “ relates to a
sort” and thus is related to our abstractions and the words
we assign to them; “our distinguishing substances into
species by names is not at all founded
on their real essences.” Inevitably the way in which we
group substances into sorts or species is based on “theirnominal,
and not by their real essences … they are made
by the mind.”
This
whole account of essences, and indeed the deliberate use of the
word essence, represents an important break from the
essentialism of the Aristotelian tradition that Locke was taught
in his youth. Aristotle believed that there are natural kinds,
the essences of which can be organised into a single hierarchical
system of classification which corresponds to the way nature is
structured. Locke rejected this claim entirely. Rather than a
unique classification open to discovery by the scientist Locke
thought it useful to classify things in lots of different ways
depending on what one wanted to do. This is quite a profound
difference. It represents an important break with the thinking of
the past and in this he was clearly influenced by natural
philosophers such as his old friend and mentor Robert Boyle. Part
of the reason for discussing words in Book III of the Essayis
precisely to break down the idea of fixed boundaries between
species or sorts of ideas. He says “these essences of
the species of mixed modes, are not
only made by the mind, but made very
arbitrarily, made without patterns, or reference to any real
existence.” In this he prefigures Charles Darwin, who needed to
dispense with the concept of fixed species of animals in order to
establish the theory of evolution by natural selection, by nearly
170 years!
It
might seem from this discussion that Locke believed that words
never retain a common meaning when they are used by one person
speaking to another, but this is not the case. Locke, the master
of common sense, was well aware that words must sometimes signify
the same meaning to different people for otherwise there would be
no communication and language would be completely useless.
However, the more complex the idea signified by the word, the
more likelihood that the word represents a different idea in the
mind of each person who hears or reads it. For the most part
Locke sees language as a tool for carrying out the pragmatic
communication necessary in everyday life. Ordinary people are the
creators of language: “Merchants and lovers, cooks and tailors,
have words wherewithal to dispatch their ordinary affairs; and
so, I think, might philosophers and disputants too, if they had a
mind to be clearly understood.”
Book
IV of the Essay, Of Knowledge in General,
brings to bear the arguments in the previous books on Locke’s
central question of what we can and cannot know. His approach is
to deal with what knowledge is, how we reach it, what the
different types of knowledge are and how certain we can be of any
knowledge we gain. He defines knowledge in terms of whether or
not one idea in our mind agrees with another (or others), thus it
is “the connexion and agreement, or disagreement and
repugnancy of any of our ideas.” This is significantly
different from Descartes’ account of knowledge which defines it
as any ideas that are clear and distinct. Here we can see why
Locke is at such pains to make it clear what he means by ideas
and their signs (words) before defining knowledge and embarking
on the central question of the Essay. He argues that
“all that we know or can affirm concerning any of” our ideas
is,
that it is, or is not the same with some other, that it does, or
does not always co-exist with some other idea in the same
subject; that it has this or that relation to some other idea;
or that it has a real existence without the mind
and
that “wherever the mind perceives the agreement or disagreement
of any ideas, there be certain knowledge.”
He
defines four sorts of agreement or
disagreement: identity, relation, co-existence (or necessary
connexion) and real existence giving the
examples:
‘blue
is not yellow,’ is of identity. ‘Two triangles upon equal
basis, between two parallels are equal,’ is of relation. ‘Iron
is susceptible of magnetical impressions,’ is of co-existence,
‘GOD is,’ is of real existence.
He
distinguishes between three types of knowledge, which have
different degrees of certainty. The clearest and most certain
isintuitive knowledge, the second most
certain demonstrative knowledge and the
third sensitive knowledge.
Intuitive
knowledge is that where “the mind perceives the agreement or
disagreement of two ideas immediately by themselves, without the
intervention of any other.” For example ‘white is not black,’
‘a circle is not a triangle,’ ‘three is greater than two.’
Demonstrative
knowledge is that where the agreement or disagreement is not
perceived immediately, but rather depends onreasoning –
following a series of steps in the mind, each of which must have
intuitive certainty, to discover the agreement or disagreement of
ideas “by the intervention of other ideas.”
Those
intervening ideas … are called proofs, and where
the agreement or disagreement is by this means plainly and
clearly perceived, it is called demonstration, it
being shown to the understanding, and the mind made see that it
is so.
Because
of all the steps involved in achieving this sort of knowledge it
is seen as “more imperfect than intuitive knowledge.” This
sort of proof is common in my discipline of mathematics, but
Locke is arguing that this type of reasoning is valid in all
areas of knowledge.
As
an illustration I am going to show you a simple demonstrative
proof of one of Locke’s examples: that if we add the three
angles in a triangle together they are the same as two right
angles. I will not use any mathematical symbols as I know this
will put off at least two thirds of my readers, but will rather
use a series of diagrams. The idea, remember, is that each step
should have intuitive certainty in order to
provide proof of the hypothesis
through reasoning and I hope that the example I
have chosen will carry you with it.
First
we remind ourselves that a right angle is the angle we find in a
square or rectangle, looking like a capital ‘L’, see [1] in
the diagram below. I am only going to show you the proof for an
acute angled triangle (one with no angles larger than a right
angle), so let’s start with a general acute angled triangle as
shown in [2]. If we take an identical triangle and turn it upside
down as shown in [3], then bring the two triangles together as in
[4] then we have the shape shown in [5] which we describe as a
parallelogram. We can see that each of the three angles a, b, c
in our original triangle appear twice in the parallelogram.
If
we look at the top left corner of the parallelogram in [5]
(labelled D in [6]), I can draw a line from there to the base of
the parallelogram to make a right angle with the base as shown in
[6]. Now what we have is a right angled triangle on the left and
a four sided figure on the right that can be separated as in [7].
The triangle can be moved over to the right hand side of the
diagram, where, because of the size of the angles it will fit
exactly onto the other figure, making a rectangle, see [9] and
[10].
Thus
we have demonstrated, by means of diagrams that the
three angles a, b, c in our original triangle, when doubled (two
triangles in [3]) have angles adding up to four right angles (in
the rectangle in [10]). Thus angles a, b and c add up to two
right angles. There are other ways of proving this, but I quite
like this diagrammatic proof by demonstration for its appeal to
our intuitive feeling for shapes and how they fit together.
The
last type of knowledge Locke discusses, sensitive knowledge, is
the least certain as it is founded on objects that enter our
minds directly through the senses. Locke is well aware of the
doubts associated with trusting our senses but, ever the
common-sense philosopher, argues strongly that it makes no sense
to reject the input we receive from the outside world. We should
accept that things in the external world have a real existence
even if our knowledge of them will always be imperfect:
The
notice we have by our senses, of the existence of things without
us, though it be not altogether so certain, as our intuitive
knowledge, or the deductions of our reason … deserves the name
of knowledge.
Continuing
on this theme, Locke claims that it is not possible for us to
discover the connection between what he describes as the primary
and secondary qualities of a substance. The
term primary qualities refers to the
‘real’ attributes of a substance, such as its size, shape and
motion while the secondary qualities are those
that we sense such as colour, taste or sound. The problem is
that, while there is no doubt a connection between these
different types of quality, nothing in the substance itself truly
resembles its secondary qualities. It is simply that the physical
attributes of the substance, its primary qualities, have “a
power to produce those sensations in us.” Thus, while arguing
that we should trust that our senses provide real, if imperfect,
knowledge of the physical world (sensitive knowledge), he also
severs the connection between simple ideas (in this case
secondary qualities) and reality.
This
leads on to a consideration of probability or
likelihood of truth. We have to accept the lack of certainty
associated with our understanding of the physical world because
of our reliance on our senses, but this does not mean that we
cannot make rational judgements about what we observe. Locke
presents an account of probable reasoning which is very similar
to the demonstrative reasoning that generates knowledge. However,
not every step in probable reasoning has intuitive certainty,
only a certain likelihood of truth. Thus when we judge an
argument or proposition as true or false we cannot guarantee that
our judgement is correct, only that it is more or less likely.
Therefore there are degrees of such judgement ranging from near
certainty to highly improbable. Locke’s discussion of probable
reasoning in the Essay does deal with things
that we can observe and experience, but his focus is on things
beyond our senses including immaterial spirits such as angels,
things too small to sense such as atoms and life on other
planets, which we cannot sense because of their remoteness from
us. However, I want to draw attention to the profound importance
of his points about probable reasoning if we are to have a true
appreciation of the strengths and limits of the scientific
method.
This
search for knowledge through probable reasoning is one way of
thinking about what the sciences are all about –when we assess
a theory or hypothesis we balance probabilities. What is more
likely? Why? At every step of an argument we should be weighing
up our level of certainty. In general, because we are rarely
dealing with ‘intuitive certainty’, the more steps, the less
certain we are of our conclusions. However, the more experiments
and observation we can perform related to each step to confirm or
refute our assumptions, the more certain we can be. This is very
important to appreciate and unfortunately is not appreciated by a
lot of scientists! It is also a huge problem for the sciences of
humanity – human beings are so complex and so different from
one another that it is surprisingly difficult to construct
general arguments about humanity that hold up to this kind of
scrutiny.
So,
what can and can’t we know? Like Descartes, Locke argues that
we can be certain of our own existence, this falling into his
category of intuitive knowledge, and we have “a demonstrative
knowledge of the existence of God.” Regarding “the real,
actual existence … of anything else, we have no other
but a sensitive knowledge.” However, there are areas of
knowledge, such as mathematics and morality, which are capable of
demonstration and thus a high level of certainty. This is because
they are closed systems in which the rules are created in our
minds – they do not depend on input from our senses. He uses
two telling examples: ‘Where there is no property, there is no
injustice,’ is certain
for
the idea of property, being a right to any thing,
and the idea to which the name injustice is
given, being the invasion or violation of that right; it is
evident, that these ideas being thus established, and these
names annexed to them, I can as certainly know this proposition
to be true, as that a triangle has three angles equal to two
right ones. Again, ‘no government allows absolute liberty’:
the idea of government being the establishment of society upon
certain rules or laws, which require conformity to them; and the
idea of absolute liberty being for anyone to do whatever he
pleases, I am as capable of being certain of truth in this
proposition, as of any in mathematics.
However,
it is difficult to establish certain truths in ethics because of
the complexity of moral ideas and this where the discussion of
language in Book III becomes most pertinent: Locke draws
attention to two ‘inconveniences’ that are a consequence of
this complexity. First, that the words we use, the ‘names’
assigned to moral ideas, are less precise than those of, say,
mathematics, thus the idea carried in one mind by a certain word
may differ from that in another mind. Secondly, that it is
difficult for the mind to remember precisely all the
relationships between different ideas and thus, especially when
several complex moral ideas are involved, it can be very
difficult to decide on the agreement or disagreement of ideas
being compared (which, remember is Locke’s definition of how we
come to knowledge). Morality does not have the advantage that
mathematics has of being able to use diagrams (and precisely
defined symbols) which allow you to review each stage of a
demonstration with ease.
Following
this train of thought, Locke moves on to the extent of our
knowledge “in respect of universality,” arguing that
only abstract general ideas can provide any sort of universal
knowledge:
If
the ideas are abstract, whose agreement or disagreement we
perceive, our knowledge is universal. For what is known of such
general ideas, will be true of every particular thing, in whom
that essence, i.e. that abstract idea is to be found: and what
is once known of such ideas, will be perpetually, and for ever
true. So that as to all general knowledge, we must search and
find it only in our own minds, and ‘tis only the examining of
our own ideas, that furnishes us with that.
Only
truths belonging to abstract ideas are eternal “as the
existence of things is to be known only from experience.” This
further underlines Locke’s arguments concerning morality for
“the truth and certainty of moral discourses
abstracts from the lives of men, and the existence of those
values in the world, whereof they treat.”
He
also warns against confusing ideas with the words we assign to
them as “the examining and judging ideas by themselves, their
names being quite laid aside” is “the best and surest way to
clear and distinct knowledge.”
In
Chapter X Locke lays out how we can be sure of the existence of
God. I will not go into the details of his argument here, but do
think it of interest to pick out two key points that lie at the
heart of his reasoning and which I think are philosophically
flawed. The first is that it is inconceivable that there was ever
a time when there was nothing – for this he appeals to our
intuitive certainty that “bare nothing” could not possibly
produce any real being. Thus there must be an eternal being
“since what was not from eternity, had a beginning, and what
had a beginning, must be produced by something else.” He goes
on to reason that “the eternal source then of all being must
also be the source and original of all power; and so this
eternal being must be also the most powerful” and also must
be a “knowing intelligent being,” as there is no other way
that humans, who are knowing intelligent beings themselves, could
have come into existence:
It
being as impossible, that things devoid of knowledge, and
operating blindly, and without any perception, should produce a
knowing being, as it is impossible, that a triangle should make
itself three angles bigger than two right ones. For it is as
repugnant to the idea of senseless matter, that it should put
into itself sense, perception and knowledge, as it is repugnant
to the idea of a triangle, that it should put into itself greater
angles than two right angles.
Like
the earlier discussion of species this argument bears an
interesting relationship to ’s theory of evolution by
natural selection, which did not come along for another 170
years. provides us with an alternative: his theory explains
how a blind process can generate sense, perception and
intelligence. I discuss this at length elsewhere, but thought it
worth drawing attention to while dealing with Locke’s ideas.
However, as with any of the great thinkers, it is also worth
remembering when Locke was writing and not take it out of
context. Locke believed in questioning everything and in not
accepting the authority either of the past or of the clergy. He
wanted people to rely on their own judgement and reasoning which
is precisely why he constructs an argument to justify believing
in God, and that is interesting in its own right. I will return
to this theme at the end of the chapter.
Having
found the bounds of human knowledge and certainty Locke turns to
the various degrees of probability or likelihood of the truth of
an idea. This is the area of human knowledge where, in the
absence of certainty, we have to apply our judgement. Here our
minds have to take ideas to agree or disagree or take some
proposition to be true or false “without perceiving a
demonstrative evidence in the proofs.”
The
highest degree of probability follows from what our own and other
people’s “constant observation has found always to be after
the same manner,” for example that fire burns. We cannot prove
that fire burns in all circumstances, but our experience and what
we know of the experience of other people gives us no reason to
doubt that it will continue to do so in conditions we have yet to
come across. These probabilities rise near to certainty and we
generally don’t distinguish between them and certain knowledge.
The second degree is when “my own experience, and the agreement
of all others that mention it, a thing to be, for the most part,
so: and the particular instance of it is attested by many
undoubted witnesses.” This degree of probability, while less
certain than the first degree, we tend to have confidence in, and
will generally be willing to act on as if it were fact. The third
degree, which is of course the weakest, is based on what Locke
calls ‘fair testimony.’ This is when we are told that
something, confirmed by witnesses, happened at a certain time and
place and, having no contradiction or reason to disbelieve the
account, we believe it.
Locke
draws attention to the difficulties associated with probabilistic
reasoning, particularly when something contradicts common
experience, or when different witnesses or histories give a
different account of events. However, we should always try as
best we can to assess the likelihood of an account for ourselves
and should not fall into the trap of discounting something which
is counter to our own experience – this may simply reflect that
our own experience is limited! This is good advice for any
scientist as much of science seems at face value to contradict
common sense (does the Earth appear flat or curved to you?) –
it is only when we investigate further (experiment, observation)
or look at the right scale that the properties or behaviour of an
object are revealed.
In
the closing chapters of the Essay Locke makes a
number of points about reason, faith and judgement which stand
today as useful guidelines for how we should approach knowledge.
He urges us to trust our own judgement and to consider the
probability of any proposition for ourselves. He makes the
interesting point that repetition of a single testimony should
give it no more weight than if it were only heard once. His point
here was primarily aimed at the word of the ancients, and had a
bearing on the general point about rejected authority and
trusting oneself. It is also another point highly relevant to the
modern era, especially in this age of instant messaging and the
web, where a single testimony can be repeated a million times
extremely rapidly without any verification of facts or truth. It
is always worth distinguishing between a variety of sources
confirming something and a number of sources repeating the same
rumour!
Locke
is explicitly against artificially formalised types of reasoning,
attacking at length the use of syllogism, a highly formal type of
argument favoured by Aristotle and his followers. Rather he makes
the case for argument from judgement as the only
sort of argument that brings true instruction and advances us in
our way to knowledge. He describes it as “the using of proofs
drawn from any of the foundations of knowledge, or probability.”
Its validity arises from it relying solely on reason,
not on respect for the reputation of some kind of authority, nor
on accepting an argument simply because we do not know a better
one.
Locke
makes a point of refuting the idea that reason is opposed to
faith, claiming that faith can never convince us of anything that
contradicts our knowledge and arguing that, except in the case of
divine revelation, we should always look first to our ownreason.
Thus anything worldly and open to our own deduction, observation,
experiment or experience must always be a matter of reason. The
only times where it is appropriate to resort to faith alone is in
areas not open to our enquiry such as whether there is an
afterlife or whether angels exist.
C
J M Hewett, November 2006
Source
Locke,
John (2004) An Essay Concerning Human Understanding,
Penguin Classics
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Tuesday 19 April 2016
The Scientific Revolution and Enlightenment John Locke’s Theory of Knowledge
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