Running head: JUSTIFIED TRUE BELIEF
Is Justified True Belief Knowledge?
Student’s Name
Institutional Affiliations
Course
1
JUSTIFIED TRUE BELIEF
2
Is Justified True Belief Knowledge?
Essay Summary on Conclusion and Premise
Approaches have been laid to determine the conditions that are necessary for a person
to know a given subject matter. This entails questioning the discretion on whether justification
is essential for knowledge. The knowledge claimed can be true or false in the long run, and it
is something that we should understand. Our conviction in belief according to the text may
stand a chance of being disputed, and that is why one may hold a truthful justification from a
wrong proposition.
Contentment of all conditions for a proposition rationalizes credence by ensuring
adequate evidence is provided to justify an actuality. The affiliation that exists between
conditions compliments the aptitude of some truth to be acknowledged or not. When one
condition entails one or more other conditions, the likelihood of accepting a certain fact is
amplified. This means that a proposition needs to be validated by parties; the source and the
receiver. Many cases are presented where one condition is sufficiently capable of maximizing
a truth as long as other conditions are related to the success or failure of the truth-seeking
procedure. In certain realities of life, certain conditions for validation of the truth in a
proposition require different approaches. At times, each approach could sufficiently add up to
the total realization of the need for truth for a certain proposition. For the success of a
conclusion relating to different conditions, one may need to examine wider conditions for
which a trustworthy conclusion can be drawn.
The conclusion may depend on luck despite the satisfaction of all the conditions. This
is common in politics, and you could find that the favorite and popular candidates lose the vote
to the silent and reserved candidates. This gesture outlives the truth that since the candidates
are popular in the polls, they have to win. In our example, popularity does not match with the
vote in the long run, but it is the voters who cast their votes that count. Justified true belief may
not necessarily be known but it is the conclusion that is derived from the premise proposition
that in the end matters. In summary, this argument is valid, and we are only questioning its
soundness. Knowledge, on the other hand, is rooted in discussions that are valid and sound.
Gettier Counter example
In his paper, Edmund Gettier relates the distinction between conditions that are
necessary and conditions that are sufficient. He deploys an example to show this venture,
whereby he illustrates that supposedly that X is true, the Y also presumes to be true. This
tabulation extrapolates that the truth of X is subject to that of Y, philosophers then say that X
is a sufficient condition for Y’s occurrence. Assume, on the other hand, X is false, Y too will
be wrong; this shows that the truth of X is necessary for Y's reality. This is then a necessary
condition perception, and in the above example, X entails Y.
Getter makes it clear that justification does not entail coincidence or fluke. In short,
luck and coincidence do not acknowledge the truth in what is perceived as knowledge.
Additionally, Getter supports the fact that a person can believe in a false proposition. What this
statement means is that one can be justified into thinking that a false hypothesis is true. This
poses a challenge to JTB by limiting the sufficiency and necessity of certain conditions. In such
circumstances, one may generate a factual deduction from a false proposition.
Gettier
In Edmund Gettier’s essay, “Is Justified True Belief Knowledge,” Gettier argues that JTB (Plato’s theory of
Justified True Belief) does not necessarily guarantee knowledge. This means that the necessary but not the
sufficient conditions for “S knows P” to be true have been met. What follows is a discussion of necessary and
sufficient conditions, the conditions that satisfy JTB, and Gettier’s reasoning of why JTB does not necessarily
guarantee knowledge.
A necessary condition for some state of affairs P is a condition that must be satisfied in order for P to obtain.
For example, what are the necessary conditions (P) that must be satisfied in order for some student (S) to pass a
course at some college or university? Let’s say that those necessary conditions for S to pass are:
(1) S must submit all of their assignments, and
(2) take all of the exams and quizzes.
However, submitting all of the assignments and taking all of the exams and quizzes will not guarantee that S
will obtain P (pass the course). So how can S guarantee that they will pass the course? The conditions that will
guarantee that’s S will pass the course are referred to as sufficient conditions. A sufficient condition for some
state of affairs P is a condition that, if satisfied guarantees that P obtains. For example, the sufficient conditions
for P are:
(1) S must get a passing grade on all assignments, and
(2) pass all of exams and quizzes.
If these conditions are satisfied, this guarantees that S will pass the course.
Gettier claims that “JTB” does not necessarily guarantee knowledge even if the following conditions are
satisfied. What are these conditions? One is said to have Justified True Belief (knowledge) if the following
conditions are satisfied:
(a) the proposition must be true (for example, the proposition, “If a student obtains a passing
grade on all assignments and passes all exams and quizzes, then that student will pass the
course)
(b) one must believe that the proposition is true, and
(c) one must be justified in believing that the proposition is true.
Similarly, S knows P if and only if:
(a) P is true
(b) S believes that P is true, and
(c) S is justified in believing that P is true.
It is important to note that justification does not entail luck or coincidence. One must be justified rightly. This
means that coincidence and luck are not considered as justificatory evidence in the establishment of what we
consider as knowledge.
Gettier provides two counterexamples that supports his claim that JTB does not necessarily result in knowledge.
In the first counterexample, two men, Jones and Smith, have applied for a certain job. Let’s suppose that Smith
is ‘justified’ in believing that the following proposition is true: Jones will get the job, and Jones has ten coins in
his pocket. We don’t know why Smith is so confident that Joes will get the job. Perhaps, someone in human
resources or Jones, himself, has advised Smith of these state of affairs. Secondly, Smith knows that Jones has
ten coins in his pocket. Therefore, Smith is justified in deducing the following proposition: Whoever gets the
job has ten coins in his pocket.
1
But Jones does not get the job. Smith gets the job. But amazingly, Smith, unknown to him, has ten coins in his
pocket. Therefore, the proposition, ‘Whoever gets the job has ten coins in his pocket’ is true. Let’s look at
Gettier’s reasons for asserting that in an instance where JTB does not guarantee knowledge.
Gettier claims that a person can believe in a proposition that is indeed false. The conjunctive proposition, ‘Jones
will get the job, and Jones has ten coins in his pocket’ is false because Jones did not get the job. We know that a
conjunction is false if even one of its constituent sentences is false. Smith knew that Jones has ten coins in his
pocket. He is also justified in believing that Jones was going to get the job. But, Jones did not get the job.
Therefore, Smith is justified in believing in a proposition that is false.
This is important because critical to the truth of proposition S knows P is the truth of proposition S is
justified in believing that P. Therefore, ‘S is justified in believing that P’ is a necessary condition of S
knows P. Reiterating, the proposition ‘Jones will get the job, and Jones has ten coins in his pocket’ is false
even though S (Smith) is justified in believing that this proposition is true.
Gettier’s second claim is that if one deduces proposition B (that is true) from proposition A (that is false), one is
still justified in believing that B is true. Smith deduced that ‘Whoever gets the job has ten coins in his pocket’
from the conjunctive proposition, ‘Jones will get the job, and Jones has ten coins in his pocket’. We know that
this proposition is false. Therefore, one can see that this deduction was made from a proposition that is false.
All of the conditions for JTB were satisfied: (1) the proposition ‘Whoever gets the job has ten coins in his
pocket’ is true; (2) Smith believed that ‘Whoever gets the job has ten coins in his pocket’; and (3) Smith was
justified in believing that ‘Whoever gets the job has ten coins in his pocket’. However, one cannot claim that S
knows P because Jones did not get the job; Smith got the job; and Smith did not know he had ten coins in his
pocket. He was only right via luck or coincidence.
Similarly, in the second counterexample, Gettier provides the following scenario. Smith knows that Jones owns
a Ford. The justification for this belief is that Jones has owned a Ford for as long as Smith has known him.
From this proposition, Smith constructs the following disjunctive propositions that speculate on the
whereabouts of a friend Brown even though he has no idea where Brown is:
(a) Either Jones owns a Ford, or Brown is in Boston;
(b) Either Jones owns a Ford, or Brown is in Barcelona;
(c) Either Jones owns a Ford, or Brown is in Brest-Litosvk.
But let’s suppose that Jones does not own a Ford and is driving a rental. Additionally, Brown, unbeknownst to
Smith, is in Barcelona. This means that disjunctive proposition (b) is true. It is not true based the proposition
that “Jones owns a Ford’. We know that a disjunction is true if just one of its constituent sentences is true. It is
true because of the proposition ‘Brown is in Barcelona’. This means that all of the conditions for JTB are
satisfied: (1) the proposition, ‘Either Jones owns a Ford, or Brown is in Barcelona’ is true; (2) Smith believed
that the proposition ‘Either Jones owns a Ford, or Brown is in Barcelona’ is true; and (3) Smith is justified in
believing that ‘Either Jones owns a Ford, or Brown is in Barcelona’ is true. But it does not result in knowledge
because it is not true that S knows P. Smith did not know of Brown’s whereabouts and, apparently, he did not
know that Jones no longer owned a Ford. He does not know P. He is right only via luck or coincidence.
In conclusion, Gettier claims that JTB does not necessarily guarantee knowledge because (1) one can be
justified in believing in a proposition that is false. This is problematic for JTB because S believing that P is a
necessary and sufficient condition for S knows P. And, (2) one can be justified in deducing true conclusion
from a false proposition.
2
“Is Jus'fied True Belief Knowledge?”
Edmund Ge;er
Before we can ‘unpack’ the argument posed by Ge;er in “Is
Jus'fied True Belief Knowledge,” we must understand the
following:
What is epistemology?
Who is Plato, Chisholm, and Ayer?
What is JTB (Jus'fied True Belief)?
What is meant by necessary condi'ons?
What is meant by sufficient condi'ons?
What is jus'fica'on?
What is meant by entailment?
What is epistemology?
Epistemology is the study of knowledge. Epistemologists
concern themselves with a number of tasks, which we might sort
into two categories.
First, we must determine the nature of knowledge; that is,
what does it mean to say that someone knows, or fails to
know, something?
Second, we must determine the extent of human
knowledge; that is, how much do we, or can we, know?
(h?p://www.iep.utm.edu/epistemo/)
Who is Plato, Chisholm, and Ayer?
Plato is one of the world's best known and most widely read and studied
philosophers. He was the student of Socrates and the teacher of Aristotle, and he
wrote in the middle of the fourth century B.C.E. in ancient Greece. Though influenced
primarily by Socrates, to the extent that Socrates is usually the main character in many
of Plato's wriMngs, he was also influenced by Heraclitus, Parmenides, and the
Pythagoreans. h?p://www.iep.utm.edu/plato/
Roderick Milton Chisholm (1916 – 1999) is widely regarded as one of the most
creaMve, producMve, and influenMal American philosophers of the 20th Century.
Chisholm worked in epistemology, metaphysics, ethics, philosophy of language,
philosophy of mind, and other areas. h?p://plato.stanford.edu/entries/chisholm/
Sir A. J. Ayer, in full Sir Alfred Jules Ayer (1910 – 1989) was BriMsh philosopher and
educator and a leading representaMve of logical posi'vism through his widely read
work Language, Truth, and Logic (1936). Although Ayer’s views changed considerably
aWer the 1930s, becoming more moderate and increasingly subtle, he remained loyal
to empiricism, convinced that all knowledge of the world derives from sense
experience and that nothing in experience jusMfies a belief in God or in any other
extravagant metaphysical enMty.
h?p://www.britannica.com/EBchecked/topic/46462/Sir-‐AJ-‐Ayer
What are necessary and sufficient condi'ons?
A necessary condiMon for some state of affairs P is a condiMon that must be
saMsfied in order for P to obtain. For example, what are the necessary
condiMons P that must be saMsfied in order for some student S to pass a
course at some college or university? The student must:
(1) submit assignments in a 'mely manner
(2) take all of the exams and quizzes
This means that if the student S does not submit the assignments in a Mmely
manner and take all of the exams and quizzes, student S will not pass the
class.
What are necessary and sufficient condi'ons? (Contd.)
A sufficient condiMon for some state of affairs P is a condiMon that, if
saMsfied, guarantees that P obtains. For example, what are the sufficient
condiMons P that must be saMsfied to guarantee some student S will pass a
course at some college or university? The student must:
(1) get a passing grade on all assignments
(2) pass all exams and quizzes
This means that if the student S gets a passing grade on all assignments and
passes all exams and quizzes, this will guarantee that student S will pass the
class.
What is jus'fica'on?
Loosely speaking, jus'fica'on is the reason why someone (properly) holds the belief,
the explanaMon as to why the belief is a true one, or an account of how one knows
what one know.
h?ps://www.princeton.edu/~achaney/tmve/wiki100k/docs/
Theory_of_jusMficaMon.html
Accidental truth, accidental jusMficaMon, or “luck” are considered as jusMficaMon.
What is entailment?
Entailment means that if P entails Q, then where P is true, Q is true; and Q is the
logical consequence of P. For example, the proposiMon ‘Joe has a car and John has a
new job’ entails the proposiMon ‘Joe has a car’. This means that ‘Joe has a car’ is the
logical consequence of ‘Joe has a car and John has a new job’. Similarly, the
proposiMon ‘Mary is a student’ entails the proposiMon ‘Mary is a student or Molly is a
teacher’…
Ge;er’s Argument
Premise 1: ‘S being jus'fied in believing that P’ is a necessary condiMon for ‘S
knows P’ though it is possible for S to jusMfied in believing a
proposiMon that is false.
Premise 2: S is jusMfied in believing in proposiMon Q that is entailed in
(or a logical consequence consequence of) proposiMon P, which S
believes to be true.
Conclusion: JTB (JusMfied True Belief) does not necessarily fulfill the sufficient
condiMons that guarantee the truth of the proposiMon that S
knows P.
Ge;er Counterexample I
Proposi'on : Jones is the man who will get the job, and Jones has ten coins
in his pocket.
Conclusion: The man who will get the job has ten coins in his pocket.
Analysis:
1. Smith gets the job.
2. Smith, unknown to him, also has ten coins in his pocket.
3. The conclusion is true but it was derived from a false premise.
4. The proposi'on is a conjunc'on and the first conjunct
(Jones is the man who will get the job) is false. Therefore,
the conjunc'on/premise is false.
5. All of the condi'ons of JTB were sa'sfied, but it didn’t guarantee
that ‘S knows P’.
6. Smith does not know that the conclusion because he did not know
how many coins were in his pocket. He based his belief on how
many coins Jones had in his pocket, “whom he falsely believes to be the
man will get the job.”
Counterexample 1
d: Jones is the man who will get the job, and Jones (the man who will get
the job) has ten coins in his pocket.
e: The man who will get the job has ten coins in his pocket.
a: Jones is the man who will get the job.
b: Jones has ten coins in his pocket.
a & b
False
∴b
True
Ge;er Counterexample II
Premise: Jones owns a Ford.
(Each of the following proposi'ons is entailed by the proposi'on: Jones owns a Ford.
Therefore, Smith is jus'fied in believing that all of the following proposi'ons are true
based on his belief that ‘Jones owns a Ford’.
Conclusion: (a) Either Jones owns a Ford, or Brown is in Boston;
(b) Either Jones owns a Ford, or Brown is in Barcelona;
(c) Either Jones owns a Ford, or Brown is in Brest-‐Litovsk.
Analysis:
1. Jones does not own a Ford.
2. Smith does not know where Brown is and unknown to him, Brown is in
Barcelona.
3. Smith derived ‘b’ from a false premise because Jones no longer owns a Ford.
4. The proposi'on ‘b’ is true because if at least one disjunct is true, the
disjunc'on is true.
5. All of the condi'ons of JTB were sa'sfied, but it didn’t guarantee
that ‘S knows P’.
6. Smith didn’t know that the proposi'on ‘b’ is true even though ‘b’ is true, he
believed it to be true, and he was jus'fied in believing ‘b’ is true.
Counterexample 2
a: Jones owns a Ford.
b: Brown is in Boston
c: Brown is in Barcelona.
d: Brown is in Brest-‐Litosvk.
a
∴[(a v b) v (a v c) v (a v d)]
F T F
False
True
Is Justified True Belief Knowledge?
Author(s): Edmund L. Gettier
Reviewed work(s):
Source: Analysis, Vol. 23, No. 6 (Jun., 1963), pp. 121-123
Published by: Oxford University Press on behalf of The Analysis Committee
Stable URL: http://www.jstor.org/stable/3326922 .
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ANALYSIS
23.6
JUNE 1963
IS JUSTIFIEDTRUE BELIEFKNOWLEDGE?
By EDMUND L.
GETTIER
ARIOUS attemptshave been madein recentyearsto statenecessary
and sufficientconditionsfor someone'sknowing a given proposition.
The attempts have often been such that they can be stated in a form
similarto the following:'
IFF
(a) S knows that P
(i) P is true,
(ii) S believes that P, and
(iii) S is justifiedin believing that P.
For example, Chisholm has held that the following gives the necessary
and sufficientconditions for knowledge:2
IFF
(i) S acceptsP,
(b) S knows that P
(ii) S has adequateevidence for P,
and
P
is
true.
(iii)
Ayer has statedthe necessaryand sufficientconditionsfor knowledge as
follows :
V
(c) S knows that P
IFF
(i) P is true,
(ii) S is sure that P is true, and
(iii) S has the right to be sure that P
is true.
I shall argue that (a) is false in that the conditions stated thereindo not
constitute a siftcient condition for the truth of the proposition that S
knows that P. The same argument will show that (b) and (c) fail if
'has adequateevidence for' or 'has the right to be sure that' is substituted for 'is justifiedin believing that' throughout.
I shall begin by noting two points. First, in that sense of' justified'
in which S's being justifiedin believing P is a necessarycondition of
S's knowing that P, it is possible for a person to be justifiedin believing
a proposition that is in fact false. Secondly, for any proposition P, if
S is justifiedin believing P, and P entails Q, and S deduces Qfrom P
and acceptsQ as a resultof this deduction,then S is justifiedin believing
Q. Keeping these two points in mind, I shall now present two cases
1 Plato seems to be considering some such definition at Theaetetus201, and perhaps
accepting one at Meno98.
2 Roderick M.
Chisholm, Perceiving:a PhilosophicalStudy,Cornell University Press (Ithaca,
New York, 1957), p. 16.
Macmillan (London, 1956), p. 34.
3 A. J. Ayer, The Problemof Knowledge,
121
122
ANALYSIS
in which the conditions stated in (a) are true for some proposition,
though it is at the same time false that the person in question knows
that proposition.
CaseI:
Suppose that Smith and Jones have applied for a certainjob. 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 supposethat Smith sees the entailmentfrom (d) to (e), and accepts
(e) on the grounds of (d), for which he has strong evidence. In this
case, Smith is clearlyjustifiedin 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 justifiedin believing that (e) is true. But it is equallyclear
that Smith does not knowthat (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'spocket, 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.
CaseII:
Let us suppose that Smith has strong evidence for the following
proposition:
(f) Jones owns a Ford.
Smith'sevidence might be that Jones has at all times in the past within
Smith's memory owned a car, and always a Ford, and that Jones has
just offered Smith a ride while driving a Ford. Let us imagine, now,
that Smith has another friend, Brown, of whose whereabouts he is
totally ignorant. Smith selects three place-namesquite at random, and
constructs the following three propositions:
(g) Either Jones owns a Ford, or Brown is in Boston;
CIRCULARITY
AND
INDUCTION
123
(h) Either Jones owns a Ford, or Brown is in Barcelona;
(i) Either Jones owns a Ford, or Brown is in Brest-Litovsk.
Each of these propositionsis entailedby (f). Imaginethat Smithrealizes
the entailmentof each of these propositions he has constructedby (f),
and proceeds to accept (g), (h), and (i) on the basis of (f). Smith has
correctlyinferred(g), (h), and (i) from a proposition for which he has
strong evidence. Smith is therefore completely justified in believing
each of these three propositions. Smith, of course, has no idea where
Brown is.
But imagine now that two further conditions hold. First, Jones
does notown a Ford, but is at presentdrivinga rentedcar.And secondly,
by the sheerest coincidence,and entirely unknown to Smith, the place
mentionedin proposition(h) happensreallyto be the placewhereBrown
is. If these two conditions hold then Smith does not know that (h) is
true, even though (i) (h) is true, (ii) Smith does believe that (h) is true,
and (iii) Smith is justifiedin believing that (h) is true.
These two examplesshow that definition(a) does not state a suffiient
condition for someone's knowing a given proposition. The same cases,
with appropriatechanges, will suffice to show that neither definition
(b) nor definition(c) do so either.
WayneState University
CIRCULARITYAND INDUCTION
By PETER ACHINSTEIN
1. DECENTLY' I suggested why an argument proposed by Max
Black, which attempts to support an inductive rule by citing
its past success,suffersfrom circularity.The inductiverule under
discussionis this:
R: To argue from Mostinstances
of As examinedundera widevarietyof
havebeenB to (probably)ThenextA to beencountered
conditions
willbe
B.
The argumentin favour of the rule is as follows:
(a): In most instancesof the use of R in argumentswith truepremisses
examinedin a wide variety of conditions, R has been successful.
Hence(probably):
In the next instanceto be encounteredof use of R in an argument
with a true premiss,R will be successful.
I"
The Circularityof a Self-Supporting Inductive Argument ", ANALYSIS,22.6 (June 1962).
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