[Music]
I'm Jeff pen I teach at Northern
Illinois University and this is an
introduction to critical thinking in
this lesson we're going to talk about
three things first what is critical
thinking second what is an argument
the third what's the difference between
deductive and amplia t'v arguments okay
so what is critical thinking well
fundamentally critical thinking is about
making sure that you have good reasons
for your beliefs what does that mean so
suppose that you and your friend are
talking about who's gonna be at
tonight's party and she says to you
quite confidently Monty won't be at the
party you're not sure whether or not to
believe her so it would be natural for
you to follow up by asking why do you
think so and there are a lot of
different things that she might say in
response we're gonna talk about three
possible answer she could give first she
might say I can't stand him I want to
have a good time second she might say
well he's really shy and he really goes
to parties and third she might say he's
in Beijing and it's impossible to get
here from Beijing in an afternoon the
first response that she gives you does
not give you a good reason to believe
that Monty won't be at the party the
second reason though is a good reason to
believe the module if he's really shy
and rarely goes to parties
then it's probable that he won't be at
tonight's party similarly the third
reason also gives you a good reason to
believe that Monty won't be at the party
if he's in Beijing and it's impossible
to get here from Beijing in an afternoon
then it's guaranteed that he won't be at
the party and when you notice things
like that when you distinguish between
good and bad reasons for believing
something you're exercising your
critical thinking skills
so critical thinking is making sure we
have good reasons for our beliefs and so
one of the essential skills that you
learn when you're studying critical
thinking is how to distinguish good
reasons for believing something from bad
reasons for believing something well
it's worth saying something about how
I'm using the term good here I'm not
using it to indicate anything having to
do with morality or ethics so it's not
morally right or morally good to believe
something on the basis of good reasons
similarly it's not morally wrong or evil
or wicked to believe something on the
basis of a bad reason rather hear what
it is to say that a reason is good is
closely tied to the notion of truth so a
good reason for belief is one that makes
it probable that is it's one that makes
the belief likely to be true the very
best reasons for a belief make it
certain they guarantee it so why does
this matter well the reason that
critical thinking is important is
because since we're rational we want our
beliefs to be true rational people want
to have true beliefs and we want not to
have false beliefs and the best way to
to be rational in this way inste form
beliefs only when you find good reasons
for them okay that leads us to our
second question what is an argument an
argument is a set of statements that
together comprise a reason for a further
statement so for example we can consider
one of your friends responses before as
an argument she's given you two
statements
Monte's really shy and Monty rarely goes
to parties which together comprise a
reason for believing that Monty won't be
at the party the statements that are the
reason we call the arguments premises so
Mach is really shy as premise one monkey
rarely goes to parties as premise two
and the statement that those premises
give you reason to believe we call the
arguments conclusion
a good argument is one in which the
premises give you a good reason for the
conclusion that is the premises make the
conclusion likely to be true in that
case we say that the argument supports
the conclusion good arguments support
their conclusions the bad arguments
don't support their conclusions so a key
part of critical thinking is learning to
evaluate arguments to determine whether
or not they're good or bad that is
whether or not their premises support
their conclusions the read argument is
the first response that she gave to
premises I can't stand Monty and I want
to have a good time when the conclusion
is Monty won't be at the party and the
third argument which we'll put in purple
consisted also two premises Monty's in
Beijing and he can't get from Beijing to
the party in time so he won't be at the
party now as I indicated before the
first argument is not good
well the purple argument is good and
here I can explain a little bit more
about why if you consider what the red
arguments premises say that your friend
can't stand Monty and she wants to have
a good time and think about their
relationship to the conclusion of the
argument you'll see that those
statements don't make that conclusion
any more likely to be true the fact that
your friend can't stand Montaigne wants
to have a good time doesn't do anything
to make it more likely that Monty won't
be there it's simply unrelated to the
conclusion in the purple argument though
the premises if they're true they
guarantee that the conclusion is true so
they make it very probable the truth of
the premises guarantees the truth of the
conclusion and so in the purple argument
the premises do you support the
conclusion now it's worth pointing out
that the red argument though it's bad as
it stands could be made a good argument
with the addition of some background
premise so for example if you found out
that your friend was the person who
decided who was going to be invited to
the party then the fact that she can't
stand Monty and wants to have a good
time
would give you a good reason to believe
that Monty won't be at the party because
it would give you reason to believe that
she didn't invite him but as it stands
the argument is not good those two
premises considered in themselves give
you no reason to believe that
okay our last topic is to distinguish
two different types of arguments so I'm
gonna put up here on the left the orange
argument which is the second response
that your friend gave Monte's really shy
and he really goes to parties on the
right we'll put the purple argument
bottles of Beijing if you can't get from
vision to the party in time both of them
have the same conclusion Monty Monty now
as I said before both of these are good
arguments they both do give you reason
to believe the conclusion ie both of
those premises which support the
conclusion but there's an important
difference between the two arguments
that I want to point out if you consider
the purple argument and think about what
those premises say you'll notice that if
those premises are true if Monty's in
Beijing and can't get from Beijing to
the party in time then it must be true
that Monty won't be at the party those
premises guarantee the conclusion in
such an argument where the premises
guarantee the truth of the conclusion we
call the argument deductive in a
deductive argument given the premises
the conclusion must be true just
thinking about the information and the
premises in the deductive argument gives
you all you need to deduce the
conclusion
if you look at the orange argument
though you'll notice that that's not the
case in the orange argument even if
those premises are true the conclusion
might still be false even given that
Monty's really shy and rarely goes to
parties it's still possible that he'll
get over his shyness and suspend his
policy of barely going to parties and
unexpectedly show up it's unlikely but
it's possible so the truth of the
premises in the orange argument does not
guarantee the truth of the conclusion
arguments like this we call ampliative
in an amplitude argument the truth of
the premises makes the conclusion
probable but doesn't guarantee you now
as I said both of the arguments are good
and creative arguments can often be very
good arguments they're just not
deductive the premises don't guarantee
the truth of the conclusion now when
you're evaluating an argument it can be
important to know whether or not the
argument is supposed to be deductive or
supposed to be merely amplitude if an
argument is supposed to be deductive but
careful consideration of the argument
reveals that in fact the premises don't
guarantee the truth of the conclusion
the conclusion could be false even
though the premises are true that's
often a good reason to reject the
argument as a bad argument whereas in an
AmpliTube argument to notice that the
truth of the premises doesn't guarantee
the truth of the conclusion is simply to
notice that it's an amplitude of
argument if you were to object to the
orange argument by pointing out that
still the conclusion could be false
you'd really be missing the point in an
AmpliTube argument it's taken for
granted that the conclusion is not
guaranteed by the premises rather what
an applet of argument is doing this you
have any reasons to think that the
conclusion is probable so knowing what
type of argument an argument is is
essential to knowing which tools to use
to evaluate whether or not it's a good
argument and we'll talk quite a bit more
about different tools for evaluating
both AmpliTube and deductive arguments
in future lessons
okay so summing up this lesson critical
thinking is making sure that we have
good reasons for our beliefs where we
understand a good reason as one that
makes the belief probable or likely to
be true an argument is a set of
statements which you call premises that
together comprise a reason for another
statement which we call the arguments
conclusion and in a good argument the
premises support their conclusions that
is the premises give you a good reason
for believing the conclusion because
they make it probable a deductive
argument is one where the conclusion is
guaranteed by the premises if the
premises are true then the conclusion
must be true an AmpliTube argument is
one where the premises don't guarantee
the conclusion but they do make it
probable so they can still provide you
with good reason for believing the
conclusion okay so that ends this
introductory lesson