2. The definition of knowledge: What is propositional knowledge?
Introduction
For this section of the course, you will need to know:
1. The difference between acquaintance knowledge, ability knowledge and propositional
knowledge.
2. The tripartite view of knowledge.
2.1 Issues with the tripartite view of knowledge: the conditions are not individually
necessary.
2.2 Issues with the tripartite view of knowledge: cases of lucky true beliefs (Gettier and
Fake-Barn Cases) show that the justification condition should be strengthened, added to
or replaced.
2.2.1 Responses to cases of lucky true beliefs:
- Infallibilism: the justification condition should be strengthened, and there
should be a requirement for an impossibility of doubt (Descartes).
- A ‘no false lemmas’ condition should be added.
- Reliabilism: the justification condition should be replaced with ‘produced by
a reliable process’.
- Virtue Epistemology: the justification condition should be replaced with
‘acquired as a result of a person exercising their intellectual virtues’.
1. The difference between acquaintance knowledge, ability knowledge and
propositional knowledge.

Acquaintance knowledge (knowing ‘of’) includes knowing a person, place, or thing because
we have met the person/visited the place/experienced the thing. For example:
I know Sally because I have met her.
- I know London because I visited there.
- I know the sound of Beethoven’s 5th symphony because I have heard it.
- I know the taste of coffee because I have tried it.
Importantly, acquaintance knowledge need not involve any capacity to express this knowledge in
language. For example, I may know what Beethoven’s 5th symphony sounds like without being able
to describe it or without knowing any facts about it.

Ability knowledge (knowing ‘how’ or practical knowledge) involves knowing how to do
something. For example:
- I know how to ride a bike.
- I know how to make a cup of tea.
Like acquaintance knowledge, a person may have practical knowledge of how to do something
without the capacity to express this knowledge in language. For example, I may know how to ride a
bike without being able to express the details of what this knowledge entails (the details of how to
ride a bike).

Propositional knowledge (knowing ‘that’) is knowing that something is the case. For
example:
- I know that the earth orbits the sun.
- I know that I had breakfast this morning.
- I know that I am studying AS philosophy.
Unlike the other two types of knowledge, this type of knowledge can (at least in principle) be
expressed in language; I can make statements about what the world is like. For example, when I
make the statement, ‘I know that the earth orbits the sun’ I am claiming that this is a true fact about
the world.
2. The tripartite view of knowledge.

The distinction between true beliefs and knowledge is first discussed in Plato’s dialogue, the
Meno. The character Socrates argues that:
“True beliefs are a fine thing and do all sorts of good so long as they stay in their place; but they will not stay
long. They run away from a man’s mind, so they are not worth much until you tether them by working out
the reason… Once they are tied down, they become knowledge, and are stable. That is why knowledge is
something more valuable than right belief. What distinguishes one from the other is the tether”
Plato, Meno.
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

Thus, for Plato, knowledge is more certain than belief because it is ‘tethered’ by reasons or
evidence.
In Plato’s Theaetetus he claims that ‘true belief accompanied by a rational account is
knowledge’, or in other words, knowledge is a true belief that is supported by strong reasons
or evidence.
So, the traditional view of knowledge is that it is a justified, true belief: to know a proposition
these three conditions must be met:
- The person must believe the proposition;
It must be true; and
-
The person must have justification for believing in it.
The tripartite view of knowledge:
S knows that p if and only if:
1. S believes that p
2. p is true
3. S has adequate or sufficient evidence for p, or is justified in believing that p.
e.g.
Sally knows that the earth orbits the sun if and only if:
1. Sally believes that the earth orbits the sun (the ‘psychological’ or ‘internal’ criterion).
2. It is true that the earth orbits the sun (the ‘external’ criterion).
3. Sally is justified in believing that the earth orbits the sun because she read it in a reliable science
journal.
These three conditions for knowledge are considered to be individually necessary for knowledge
(each condition must be satisfied for there to be knowledge) and jointly sufficient (if all three
conditions are satisfied then there definitely is knowledge).
3.1 Issues with the tripartite view of knowledge: the conditions are not individually
necessary.
The Belief condition
- The philosophical consensus and traditional view is that belief is necessary for knowledge as it
seems impossible for a person to know a proposition without believing that proposition. For
example, it is incoherent to say ‘I know the earth orbits the sun but I don’t believe it does’.
- Some philosophers, however, have argued that knowledge and belief are separable and others
have even argued that they are mutually incompatible.
- In Plato’s work The Republic (written later than the Meno) he adopts an incompatibilist view. In this
work he argues that knowledge is infallible (beyond reasonable doubt) whereas belief is fallible (can
be doubted) and therefore they are fundamentally different things. Knowledge entails a degree of
certainty which belief does not. Thus, knowing goes beyond mere belief.
- Additionally, people may not believe they know something until they answer a set of questions on
it and get them right due to recalling previously-learnt information; thus they don’t believe they
know the answer when they actually do.
The Truth condition
- This condition is fairly uncontroversial; it is impossible to know a proposition that is false.
- While we may claim to know something that is false, it does not mean that we actually know it (for
example people in the past claimed to know that the earth was flat but we would not call this
knowledge). Our belief must correspond with the way the world is for us to have knowledge.
The Justification Condition
- This condition is required because it is possible to have a true belief that would not, at least
intuitively, count as knowledge, e.g. lucky guesses.
- For example (p.66 of Hayward, Jones and Cardinal) if a juror believes that a defendant is guilty
purely because of the colour of their skin, and the defendant does turn out to be guilty, we would
not intuitively say that the juror had knowledge because the juror did not have good justification for
her belief (instead her belief was solely based on irrational prejudice).
- However, the strength of the justification needed has been much debated.
- Reliabilists claim that a reliable process that produces the true beliefs is what counts as knowledge
(this will be discussed further on p….)
2.3 Issues with the tripartite view of knowledge: cases of lucky true beliefs (Gettier and
Fake-Barn Cases) show that the justification condition should be strengthened, added to
or replaced.
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
Are the JTB conditions sufficient for knowledge?
In his 1967 paper, ‘Is Justified, True Belief Knowledge?’ Edmund Gettier gave examples of
justified true beliefs that we would not count as examples of knowledge.
‘Is Justified, True Belief Knowledge?’ – The example of Smith and Jones
Suppose that Smith and Jones have applied for a certain job. And suppose that Smith has strong evidence for the following
conjunctive proposition:
(d) Jones is the man who will get the job, and Jones has ten coins in his pocket.
Smith's evidence for (d) might be that the president of the company assured him that Jones would in the end be selected,
and that he, Smith, had counted the coins in Jones's pocket ten minutes ago. Proposition (d) entails:
(e) The man who will get the job has ten coins in his pocket.
Let us suppose that Smith sees the entailment from (d) to (e), and accepts (e) on the grounds of (d), for which he has strong
evidence. In this case, Smith is clearly justified in believing that (e) is true. But imagine, further, that unknown to Smith, he
himself, not Jones, will get the job. And, also, unknown to Smith, he himself has ten coins in his pocket. Proposition (e) is
then true, though proposition (d), from which Smith inferred (e), is false.
In our example, then, all of the following are true: (i) (e) is true, (ii) Smith believes that (e) is true, and (iii) Smith is justified
in believing that (e) is true. But it is equally clear that Smith does not KNOW that (e) is true; for (e) is true in virtue of the
number of coins in Smith's pocket, while Smith does not know how many coins are in Smith's pocket, and bases his belief in
(e) on a count of the coins in Jones's pocket, whom he falsely believes to be the man who will get the job.
Edmund Gettier – ‘Is Justified, True Belief Knowledge?’
As most people would claim that Smith did not have knowledge, Gettier’s example showed that
there can be cases of justified, true beliefs which we would not count as knowledge because there is
an element of luck involved, and therefore the JTB conditions are not sufficient for knowledge.
Another famous example of a Gettier-Style problem was given by Carl Ginet:
Henry is driving through the countryside and unbeknown to him he drives through Fake Barn County. This is an area filled
with Fake Barn facades. Henry fails to notice all but one of the fake barns and he forms the belief, ‘there is a barn in that
field’. However, Henry has chanced to look upon the only real barn in Fake Barn County. Thus, Henry’s belief that there is a
barn in the field is true and he is justified in believing it because he sees it. However, the context – of Henry being in Fake
Barn County – means that his justified, true belief seems to be luckily true. Therefore, this Gettier-style counter example
suggests that the JTB conditions are not sufficient for knowledge.
Thus, the JTB account of knowledge needs modification.
(See p.69 of AQA AS Philosophy, Hayward, Jones and Cardinal, for more Gettier-style examples).
i.
Responses to cases of lucky true beliefs
(a) Infallibilism: the justification condition should be strengthened, and there should be a
requirement for an impossibility of doubt.
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Infallibilists claim that the justification must be so strong that it is impossible to doubt the
truth of the proposition. So, the belief is infallible – it cannot be wrong. Therefore, we
should only accept as knowledge those things which we cannot doubt. Examples of which
might include:
- I believe that 2+2=4.
- I believe that I am currently in pain.
- I believe that a thinking thing exists.
Descartes adopted an Infallibilist approach in his Meditations.
Descartes’ approach involved him doubting all of his beliefs until he could find a belief/set of
beliefs which could not be rationally doubted. It was Descartes’ hope to find a bedrock of
infallible beliefs from which he could build a system of certain beliefs.
After using his ‘Three Waves of Doubt’ he found that the only infallible belief that remained
was Cogito ergo sum, ‘I think therefore I am.’ It was impossible to doubt this belief as in the
very act of doubting he would be thinking.
‘Some years ago I was struck by how many false things I had believed, and by how doubtful was the
structure of beliefs that I has based on them. I realised that if I wanted to establish anything in the sciences
that was stable and likely to last, I needed – just once in my life – to demolish everything completely and
start again from the foundation.’ Descartes, Meditation 1, p.1
Evaluating Infallibilism
Strengths of Infallibilism as a response to Gettier
•
•
•
Infallibilism is not open to Gettier cases
because none of the cases would count
as knowledge in the first place as they
are open to some doubt.
By restricting knowledge to only those
things that cannot be doubted then
there is no room for Gettier counter
examples to thrive as these all rely on
beliefs that are merely plausibly justified
- which might be false, but turn out to be
luckily true.
It fits with our intuition that knowledge
involves a level of certainty.
Weaknesses of Infallibilism as a response to Gettier.
•
Infallibilism implies that we have very little
knowledge – going against our intuition that
we know a lot of things.
•
Unless Descartes can build his a system of
knowledge only using infallible beliefs then
Infallibilism leads to scepticism.
•
While some philosophers might argue that our
common definition of knowledge needs such a
radical revision, others would argue that to
diverge too radically from common usage
involves our leaving behind the very concept
we set out to analyse.
•
Infallibilism seems to be prescribing what our
concept of knowledge should be, rather than
analysing/describing what it is.
(b) No False Lemmas: A no false lemmas condition should be added, so K= J+T+B+ no false
lemmas.



A lemma is a subsidiary proposition used to justify another proposition.
By adding a no false lemmas condition, knowledge becomes a justified, true belief
that has not been formed from any false propositions/beliefs.
So, in the Gettier example of Smith and Jones, Smith’s true belief that the person
who gets the job will have ten coins in their pocket was based on the false belief
that Jones would get the job. Therefore, as Smith’s belief was based on a false
lemma it cannot be knowledge.
Evaluating the no false lemmas theory.
Strengths of the no false lemmas theory as a
response to Gettier

The no false lemmas theory copes well
with the standard Gettier cases where a
true belief is based on a false belief; for
example the case of Smith and Jones.
Weaknesses of the no false lemmas theory as a
response to Gettier.


It does not cope with other Gettier-style counter
examples where there is no obvious false belief
involved in the formation of the person’s true belief.
For example, the Fake Barn Case of Henry driving
through Fake Barn County does not seem to involve
any false beliefs.
A further example can be found on p.82 of Hayward,
Jones and Cardinal:
You look up at a clock that says it is 12 O’clock and
form the belief that it is midday. However, this clock
stopped yesterday at this time. But, coincidentally it
is 12 O’clock. Therefore your belief that it is midday
is true, justified and does not seem to rely on any
false lemmas; however, we would not intuitively call
it knowledge due to the belief only being luckily
true.
The no false lemmas theory improved...

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The theory can be added to by not accepting as knowledge any justified, true belief which has been based upon
tacit or hidden false assumptions (not just false explicit beliefs/premises as in the Smith and Jones example).
So, in the clock example above, the person who forms the belief that it is midday makes the tacit assumption
that the clock is working. As this assumption is false, the person does not have knowledge to begin with and so
the Gettier problem no longer exists.
However, this improvement still does not seem to be able to solve Fake Barn Cases. In the case of Henry seeing
a real barn in Fake Barn County there do not seem to be any false lemmas or tacit false assumptions in his
formation of this belief.
The Philosopher who formulated the theory that knowledge should not involve tacit false assumptions , William
Lycan, has responded to this by arguing that there are no false assumptions in Fake Barn Cases but that these
do not count as Gettier-style counter examples as the people do actually have knowledge. So Henry does have
knowledge that there is a barn in the field, despite the lucky context in which he forms this belief.
(c) Reliabilism: the justification condition should be replaced with ‘produced by a reliable
process’ (K= R+T+B).


Knowledge is a true belief that is produced by a reliable process.
Reliabilism claims that you know that P if:
- P is true;
- You believe that p;
- Your belief is caused by a reliable process.
A reliable process is one that produces a high percentage of true beliefs.
For example, take these two cases:
- You read on www.conspiracies4ever.com that the Prime Minister is a reptile.
- You read in a broadsheet newspaper that foxes are mostly nocturnal.
You would say that you could probably know that foxes are mostly nocturnal because this
information is from a broadsheet newspaper – a reliable type of newspaper which prints a
high percentage of truths. However, you would not say that you know the Prime Minister is
a reptile because www.conspiracies4ever.com is an unreliable website that does not publish
many true beliefs.
Reliabilism is not saying that knowledge is a justified, true belief that has been formed by a
reliable process, it is saying that knowledge is a true belief that has been formed by a
reliable process; thus replacing the justification condition.
Examples of reliable processes (processes that produce a high percentage of true beliefs)
include: seeing things close up; simple arithmetic; using trustworthy sources.
Examples of unreliable processes (processes that do not produce a high percentage of true
beliefs) include: wishful thinking; beliefs formed through hallucinations/dreaming; glimpsing
things from a distance; complex mental arithmetic; remembering things from a long time
ago.
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Evaluating Reliabilism
1) Which is better: a reliable process or justification?
Reliable Process


A reliable process is easier to define than
good justification. It can be difficult to
define what is good justification and the
definition can often be circular, e.g. for a
belief to be sufficiently justified to count as
knowledge it needs to have knowledgeworthy justification. Reliabilism offers a
clear account of justification.
The theory allows animals to have
knowledge (they have evolved to develop
reliable processes of vision, memory, etc)
and grants knowledge to any reliable
process for example a man who is able to
very successfully predict the future but
does not know how.
Justification



Justification and ‘formed by a reliable
process’ are different things as
justifications are internal to the believer,
(the believer can explain why they are
justified in holding the belief) whereas
being involved in a reliable process does
not have to involve a conscious thought
process.
Reliabilism allows animals to have
knowledge, which they don’t.
Justifications involve reasons for beliefs
whereas reliable processes involve causes
(see example of John on p.89 of Hayward,
Jones and Cardinal).
2) How well does Reliabilism respond to Gettier and Fake Barn Cases?
Strengths of Reliabilism as a response to Gettier



Reliabilism deals fairly well with standard
Gettier cases – any belief that is true due to luck
is probably not going to have been formed
through a reliable process.
Reliabilism can respond to the claim that
reliable processes seem to be in place in Fake
Barn Cases by saying that the individuals do
indeed have knowledge. So, despite the lucky
context in which Henry forms the belief that
there is a barn in the field, he does have
knowledge because his perceptual process was
reliable.
Reliabilists can also respond by saying that the
reliability of a process changes according to the
context. For example, the context of being in
Fake Barn County means that simply looking at
what looks like a barns is not a reliable process
to form the belief ‘there is a barn in that field’.
Weaknesses of Reliabilism as a response to Gettier.
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

There is flexibility in how we describe processes.
For instance, in the clock example we could
define the process as either a person looking at a
clock or a person looking at a broken clock – the
former would be a reliable process whereas the
latter would not be. We might also add that a
newer clock is more reliable than an older one.
Therefore, it is not clear how, and in what detail,
a process should be described and thus it
becomes more difficult to define what counts as a
reliable process.
In Fake Barn Cases it is not always obvious that
the process is unreliable. For example, in Henry
forming the belief that there is a barn in the field,
he uses the process of seeing at a close distance;
a process we would usually class as reliable.
However, this raises the issue of how
specific/general we define the context.
(d) Virtue Epistemology : the justification condition should be replaced with ‘acquired as a result
of a person exercising their intellectual virtues’ (K=V+T+B).
 Virtue epistemology moves away from focussing on the process to focussing on the
agent (the person).
 Virtue epistemology claims that you know that P if:
- P is true
- You believe that P
- Your true belief is a result of you exercising your intellectual virtues.
 An intellectual virtue is a tendency or disposition to use the reliable process and so
more frequently gain true beliefs. For example, to trust truths in reliable broadsheet
newspapers over www.conspiracies4eva.com.
 An intellectual vice is the tendency to use unreliable processes. For example, to trust
www.conspiracies4eva.com over reliable, broadsheet newspapers.
 We tend to trust what people say if we know they use reliable processes to acquire
their beliefs and tend to distrust what people say if we know they often use
unreliable processes to acquire their beliefs.
 While Reliabilsm would claim that a person has knowledge because their true belief
is formed through a reliable process, virtue epistemology would claim that a person
has knowledge because their true belief was formed as the result of their
intellectual virtues operating in a suitable way.
A problem with virtue epistemology:


The theory is prone to standard Gettier counter examples.
For example, in the clock example, the person believes that the time is midday (which it is)
and their belief is formed through looking at a clock (a reliable process). Therefore, they
have a true belief which has been acquired through the application of an intellectual virtue.
However, the clock had stopped yesterday at midday, so the person’s belief is only
accidentally true so we would not count it as knowledge.
Ernest Sosa’s developed account of Virtue Epistemology:
Sosa used the analogy of an archer shooting an arrow to give a more nuanced account of Virtue
Epistemology.
A shot is adroit if it is skilful (might
not always hit the target if external
factors like a gust of wind are
involved).
A shot is accurate if it hits the
target (could come about
through skill or luck).
The shot is apt if it was accurate and the
accuracy was due to the shot being adroit.
Sosa applies this analogy to knowledge, claiming that:
- A belief is accurate if it is true.
- A belief is adroit if it is formed by an intellectual virtue.
- A belief is apt if it is true because of the intellectual virtue.
So, knowledge is apt belief.
Evaluating Virtue Epistemology
Strengths of Virtue Epistemology as a response
to Gettier

In general, Virtue Epistemology, copes well
with Gettier cases. Any belief that is luckily
true is not going to be an apt belief – lucky
beliefs are not true because of an intellectual
virtue. For example, Smith’s true belief that
the man who would get the job would have
ten coins in his pocket was not true because of
an intellectual virtue, therefore it cannot be
counted as knowledge. Therefore, as Smith
does not have knowledge this example is not a
problem in the first place.

One response to the problems posed by Fake
Barn Cases is to say that these are cases of
knowledge, so Henry does know that there is a
barn in the field despite the element of luck.
Another response is to say that the context in
the Fake Barn Cases means that the exercising
of an intellectual virtue is not adroit – the
context changes the level of skill needed to
have an apt belief.
Sosa argues that in Fake Barn Cases, the
believer lacks an understanding of their
context and so they are not able to judge how
apt, or not, their belief is. Because of this, he
claims that in these cases the believer has
animal knowledge but not reflective
knowledge.


Weaknesses of Virtue Epistemology as a response to
Gettier.

Virtue Epistemology deals less well with Fake
Barn Cases. For example, Henry does seem to
have an apt belief:
- his belief is true (accurate) – there is a barn
in the field;
- his belief is adroit as it was formed by an
intellectual virtue (trusting one’s senses under
normal conditions), and
- his belief is apt because it is true due to him
using his intellectual virtues.
However, many would not count this as
knowledge.