Logic in Practice Mark Pursley. What is Critical Thinking? Disagreement? Imposing our beliefs on...

Logic in PracticeMark Pursley

What is Critical Thinking?Disagreement?Imposing our beliefs

on others?Negativity?A non-creative

activity?Assumptions, claims,

and arguments.

Critical Thinking: A 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?

Obstacles to Critical ThinkingHumans 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 ThinkingEgocentricity and resistance to change. Change

can threaten our identity, our security, our sense of self-worth. 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.

RelativismWhile 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 AuthorityParents, 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 ourselvesIs 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 ThinkingPersonal 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 InterpretationsAn issue is a topic about

which 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.

Some issues are evaluative. 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 LanguageInformative: To affirm

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.

Expressive: To vent or arouse feelings.

You look marvelous!Philosophers rule!Go Trojans!Hey, hey, ho, ho,

budget cuts have got to go!

Directive LanguageTo 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 FunctionsPersuasive: 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 ConventionEffective

communication 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.

Vague terms have an 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.

DefinitionOstensive definition: to

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.

The referential criteria 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 ConditionA 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 SufficientBirth 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 MontagnierA belief’s being due to upbringing is neither necessary nor

sufficient for it to be a variance with rationality. G.A. CohenBelieving 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 Avoid1. Circularity A circular definition

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.

3. Negativity A soul is an immaterial substance.

Good definitions are neither too broad nor too narrow.

A Christian is a religious person.

A Christian is a born-again Bible-believing Baptist.

ConnotationsThe 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.