Download How can I be sure I know something?

How can I be sure I know
something?
Learning Goal:
By the end of the lesson students will begin to
understand Plato’s definition of knowledge as
true and justified belief
 We all want our beliefs to be true, connect us
to reality and not be mere opinions
 But what is real knowledge?
Attaining knowledge
 Our concept of knowledge as humans is first of all an
attainment concept
 For example, in Basketball we shoot in order to score.
Shooting is the activity, scoring is the attainment
intended.
 In the life of the mind, we believe in order to know
 So, like the basketball analogy, believing is the activity,
knowledge is the attainment
 Similarly, just as you can shoot a basketball and not
score a basket, you can believe something and not
have knowledge
What Is Knowledge?
 Putting the question this way makes the
question sound really hard. Here are three
other ways to put it:
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“What is it to know something?”
“Under what conditions is it true that a person
qualifies as knowing that something is the
case?”
 An answer to this question will be a theory of
knowledge.
Further Clarification of the Question ‘What
is Knowledge?’
Three Ways the Word ‘Knows’ Is Used:
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“Bob knows how to ride a bicycle.”
- Ability or practical knowledge
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“Bob knows Cassandra”
- Acquaintance knowledge
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“Bob knows that the earth is round.”
*Propositional knowledge, or knowledge by description
The theories of knowledge we’re looking at are about the
third kind of knowledge – called knowledge that, or
propositional knowledge (knowledge by description)
Plato on Knowledge
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The best known ancient Greek philosopher
Student of Socrates; teacher of Aristotle
Wrote about 23 philosophical dialogues
Famous doctrine: the Theory of the Forms
Western philosophy “consists of a series of
footnotes to Plato.”
- A. N. Whitehead (1929)
How can I be sure I know something?
 Plato and his colleagues came up with an
answer to the question.
 They said that for you to have certain
knowledge (prepositional knowledge) you
have to subject your knowledge claim (a
statement of what you think you know) to
three tests.
Test 1
 You must believe the statement.
You can’t know something unless you believe it. I can’t
know there is a God unless I believe that a God exists.
Belief is necessary for knowledge it is part of the
package deal.
Example: Knowledge of time
You must first believe your watch keeps accurate time in
order for you to know whether or not it does.
Test 2
 Your belief has to be true
Belief alone not sufficient for knowledge. You
can believe something that is false.
Watch example: Your watch must keep time
accurately. If it loses five minutes everyday,
then you cannot know that it keeps time
accurately your belief has to be true.
But… hold on… how do we know if
something is true??
 A great deal has been written on the nature of truth and
we will examine it in this course… later 
 Some philosophers believe there is a single, absolute
objective truth, they are called absolutists.
 Some believe that everything is subject to human
interpretation, they are called relativists because they
believe everything is relative to human understanding.
 For our purposes of Knowledge as a True Justified
Belief, we are going to go with the truth of the
absolutist, as Plato was an absolutist.
The Absolutist Definition of Truth
 Truth has three characteristics
1. Truth is public: truth is the same for everyone,
that means that if the knowledge claim is true
it is true for everyone, but if the knowledge
claim is false it is false for everyone.
Consider the time example example…
Truth is independent of anyone’s belief
 The knowledge claim may be false even if
everyone believes it is true
 The knowledge claim might be true, even if
no one believes that it is
 The truth of the statement “your dog is
friendly” is independent of whether you think
it is true or not
Truth is eternal
 A true statement is true, was true and will always
be true
 Now we have a slight problem with the dog
example. It might be that as your dog becomes
older it changes and becomes “unfriendly,” but
the current statement “your dog is friendly” is true
for now, and will be true “for now” forever. Thus if
your dog changes, the truth that he was once
unfriendly will not change.
But back to Plato’s three tests for knowing
 Recap
 For knowledge, you must believe the
statement, the statement must be true (public,
independent, eternal) and finally…
 Your true belief must be justified
Not this…
Why do we need justification?
 Because you can believe something and your belief can turn
out to be true, without you actually knowing the thing you
believed…
Suppose you conjure up a belief that right now that Barak
Obama is brushing his teeth.
Imagine you actually believe this, by force of sheer will.
Suppose even further by the force of mere coincidence alone
that Obama has just come back from a presidential lunch and
just happens to be polishing his molars ready to rinse and
spit.
You have the belief, and the belief happens to be true. Yet
you had no real evidence it was true, you just got lucky.
Philosophers deny that this is real knowledge. You did not
know Obama was brushing his teeth, it was a wild
coincidence, not an attainment of knowledge.
Knowledge = Justified True Belief
 If you were looking at a live broadcast on
CNN of Obama over his bathroom sink,
brushing away, your true belief would be
justified and thus you could count it as real
knowledge. The question “how do you
know?” would be answered by “I’m seeing it
right now on CNN.” As long as CNN is a
credible source…
What exactly is proper justification?
 Good reasons to justify your beliefs,
according to philosophers are as follows:
#1: Logic – logic is the basis for much of our
knowledge an is an important justification for
true belief
Good reasons for justification #2 Empirical
Evidence
 Empirical evidence is evidence gained by
your five sense. What your senses, perceive,
your sense perception, is one of the main
sources of your knowledge of the world. Your
five main senses are of course, sight, touch,
taste, smell and hearing
Good reason for justification #3 Memory
 Memory is notoriously fickle, but approached
with care, memory is generally reliable
Good reason for justification #4 Authority
 Of course we must be very careful who we
accept as an authority, but in our everyday
lives, we can accept that authorities do exist
and we can trust them