Mark Pursley
What is Critical Thinking?
 Disagreement?
 Critical Thinking: A
 Imposing our beliefs on
process of rational
analysis that guides a
person’s attempt to
determine whether to
accept, reject, or suspend
judgment about a claim.
 What about intuition?
others?
 Negativity?
 A non-creative activity?
 Assumptions, claims,
and arguments.
Obstacles to Critical Thinking
 Humans are not
perfectly rational
creatures,
 Psychological factors
that obstruct our ability
to determine whether a
statement is more likely
to be true or false.
I’m only human!
Barriers to Critical Thinking
 Egocentricity and resistance to change. Change can
threaten our identity, our security, our sense of selfworth. Alternative viewpoints may force us to admit
we were wrong, which is often difficult.
 Arrogance and ignorance go hand in hand.
 Wishful thinking and self deception. How we want
things to be may influence how we see them, what
evidence we select, and what we choose to ignore.
Superstitions are often maintained in this way.
Populus vult decipi*
 Ethnocentrism and
cultural conditioning.
The herd instinct,
conformism. It is easy
and natural to believe
what our group believes
and to ridicule those
who disagree.
It works for us!
* The people want to be deceived.
Relativism
 While tolerance of diversity and an open mind are virtues
for the critical thinker, crude or naïve relativism (which
holds that all opinions and actions are equally moral so
long as some individual or group approves of them) is not a
well founded position. Disagreement about controversial
issues does not entail that all positions are equally
reasonable. Relativism becomes intellectual laziness when
someone refuses to examine a practice or policy position
carefully, weighing the principles involved and the
consequences of alternative courses of action with care.
Reliance on Authority
 Parents, teachers, clergy,
politicians, celebrities,
radio and television
commentators, etc. may
persuade us to believe
things without providing
adequate evidence to
support their views.
I see you are rather gullible.
Accepting what an authority says prevents us
from thinking for ourselves
 Is the authority qualified in that field? A philosopher
is not an authority, say, on a scientific theory.
 Is there a consensus among the experts? If not, then
one can’t resolve the dispute by an appeal to authority.
 Is it theoretically possible to verify or falsify the claim?
If there is nothing that could count as evidence for or
against the claim, then the claim is vacuous.
The Value of Critical Thinking
 Personal autonomy and
self determination.
 Careful thinkers are less
likely to be duped by
persuasive
propagandists.
 They sell us everything
from youth to religion,
the same way they sell us
our wars. J Browne
 Political democracy and
individual freedom.
When the persuasive
power of political
propaganda, rather that
the considered
judgments of well
informed voters,
determines social policy,
democracy is lost.
Facts, Values, and Interpretations
 An issue is a topic about which
 Some issues are evaluative.
reasonable people may differ.
Issues concern questions that
generate conflicting views that
are rationally defensible.
 Some issues are factual. Is
global warming occurring? Does
marijuana have medical
benefits? These are empirical
disputes that can be resolved by
investigating the relevant facts.
These involve disputes over
value judgments. Should the US
require more stringent fuel
efficiency standards for vehicles?
 Should the US legalize marijuana
for medicinal use?
 Value judgments involve factual
claims but are not always
resolvable by factual
investigation.
 Interpretive issues concern how
events (or texts) are to be
understood, what they mean.
Functions of Language
 Informative: To affirm or
 Expressive: To vent or
deny statements.
 Paula has left American
Idol.
 Vegans do not eat eggs.
 Barbara Boxer is the first
female president of the
United States.
 Life exits on other
planets.
arouse feelings.
 You look marvelous!
 Philosophers rule!
 Go Trojans!
 Hey, hey, ho, ho, budget
cuts have got to go!
Directive Language
 To direct the behavior of
a reader or listener.
 Eat your broccoli!
 Chill out!
 I’ll pick you up at 8:00,
be ready!
Turn or burn, sinners!
Language Functions
 Persuasive: To influence
others.
 Don’t you want to be
strong like mommy?
 Stress kills, dude!
 If you go out with me I’ll
smog certify your car for
free!
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Meaning:
A Matter of Convention
 Effective communication
 Vague terms have an
requires precision and
clarity. Two obstacles to
clear communication are
ambiguity and
vagueness.
 Ambiguous terms or
phrases have multiple
meanings: bank; bark;
cool; free,; ball; etc.
indefinite extension, so it
is not always clear what
the term applies to and
what it does not.
 Bald, natural, soon,
liberal, art, etc. The
boundaries that define
membership in these
classes are fuzzy.
Definition
 Ostensive definition: to
 The referential criteria
define by example, gives
(part of) the extension of
a term, or its reference,
that is, the objects
referred to by the term.
 Essential definition:
provides the
characteristics a thing
must have to be referred
to by the term.
are the rules or standards
by which we determine if
an object is referred to by
a particular term.
 Providing essential
definitions for terms like
pornography, obscenity,
terrorism, knowledge,
free will, art, etc. can be
complex.
Guidelines for Essential
Definitions
 Gives both necessary and sufficient conditions for the
term’s extension.
 Necessary condition: a characteristic required for
membership in the term’s extension.
 X is a necessary condition for y whenever y cannot
occur without the occurrence of x. Water is a
necessary condition for life; oxygen is a necessary
condition for fire; being male is a necessary condition
for being the pope; possessing the capacity for rational
thought is a necessary condition for being a person.
Sufficient Condition
 A characteristic that is
itself adequate for
membership in the
terms extension.
 X is a sufficient
condition for y
whenever the occurrence
of x is all that is required
to bring about y.
 Decapitation is a
sufficient condition for
bringing about one’s
death. Having five
quarters is a sufficient
condition for having
more than a dollar.
Being born in California
is a sufficient condition
for being a US citizen.
Necessary and Sufficient
 Birth control is a necessary but not a sufficient answer to





overpopulation. (Garrett Hardin)
The presence of the HIV virus is neither a necessary nor a sufficient
condition for contracting AIDS. Luc Montagnier
A belief’s being due to upbringing is neither necessary nor sufficient for
it to be a variance with rationality. G.A. Cohen
Believing in God is neither a necessary nor a sufficient condition for
calling oneself a Christian.
Citizenship is neither a necessary nor sufficient condition for American
identity and American identity is neither a necessary nor sufficient
condition for citizenship. Devon Carbado
Being female is necessary but not sufficient for becoming pregnant.
3 Things to Avoid
 1. Circularity
 3. Negativity A soul is
 A circular definition
an immaterial substance.
 Good definitions are
neither too broad nor
too narrow.
 A Christian is a religious
person.
 A Christian is a bornagain Bible-believing
Baptist.
defines a word in terms
of itself. A just law is a
law that is free from
injustice. A cordless
phone is a telephone
without a cord.
 2. Obscurity Death is
the cessation of one's
participation in finitude.
Connotations
 The connotation of a term is its intension, the
characteristics which define its extension, eg. the
specific characteristics a piece of furniture must have
to be a chair.
 Many terms also have emotional connotations and are
used to influence our thinking. Scholar/bookworm;
athlete/jock; party animal/drunk; spin doctor/liar;
fetus/unborn child; freedom fighter/terrorist. Two
words may refer to the same objects but have different
emotional impacts.