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Dr. Robert Barnard

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Philosophy 103 Linguistics 103 Yet, still, Even further More Introductory Logic: Critical Thinking. Dr. Robert Barnard. You earned it!. New Policy: All phones and digital/cellular communication devices must be off. ON PAIN OF POP QUIZ. …tell your pals – no more warnings…. Last Time :. - PowerPoint PPT Presentation

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Page 1: Dr. Robert Barnard
Page 2: Dr. Robert Barnard

Philosophy 103Linguistics 103

Yet, still, Even further MoreIntroductory Logic:

Critical ThinkingDr. Robert Barnard

Page 3: Dr. Robert Barnard

You earned it!

New Policy:

All phones and digital/cellular communicationdevices must be off. ON PAIN OF POP QUIZ.

…tell your pals – no more warnings…

Page 4: Dr. Robert Barnard

Last Time:• Laws of Thought: Philosophical

Issues about the status of logical laws.

• Meaning– Types of Meaning: Cognitive/Emotive– Intension vs. Extension– Ambiguity and Precision– Names vs. Descriptions

Page 5: Dr. Robert Barnard

Plan for Today

• Talk about Definitions• Time Permitting: Return to the issue of logical

form…

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Definitions:

• Parts of a Definition–Definiendum: The word or term or

concept to be defined–Definiens: the word or group of words

which are used to define (assign a meaning to) another term or concept

Page 7: Dr. Robert Barnard

Types of Definitions

•Lexical•Precising•Theoretical•Persuasive

Page 8: Dr. Robert Barnard

Lexical Definition

A Lexical Definition reports or describes how a term is actually used in a language.

Sometimes a term has more than one definition.-

Page 9: Dr. Robert Barnard

The ‘Idea’ of a definitioni·de·a (ī-dē'ə)

n. Something, such as a thought or conception, that potentially or actually exists in the mind as a product of mental activity.

1. An opinion, conviction, or principle: has some strange political ideas.2. A plan, scheme, or method.3. The gist of a specific situation; significance: The idea is to finish the project

under budget.4. A notion; a fancy.5. Music A theme or motif.6. Philosophy

1. In the philosophy of Plato, an archetype of which a corresponding being in phenomenal reality is an imperfect replica.

2. In the philosophy of Kant, a concept of reason that is transcendent but nonempirical.

3. In the philosophy of Hegel, absolute truth; the complete and ultimate product of reason.

7. Obsolete A mental image of something remembered.

There are at least 3 specific philosophical definitions!!!

Page 10: Dr. Robert Barnard

Precising DefinitionA Precising Definition is designed to reduce the

vagueness of a term in use. This is a kind of stipulative definition.

Example: Tom is rich. (What does ‘rich’ mean?)

…we might extend the lexical definition by adding that here ‘rich’ means “has more than 5 million dollars.” This makes the term PRECISE in our context.

Page 11: Dr. Robert Barnard

Theoretical Definition

A THEORETICAL DEFINITION assigns (stipulates) a meaning to a term by suggesting a theory that gives a certain characterization of the entities the theory denotes.

Theoretical definitions are common in mathematics and science. They fix the meaning of a term for a specific use.

Page 12: Dr. Robert Barnard

Examples: Theoretical Definitions

Geometry: “Parallel straight lines are straight lines which, being in the same plane and being produced indefinitely in both directions, do not meet one another in either direction. ” (Euclid Elements I, Def 23)

Chemistry: “An electron is a stable fundamental atomic particle with almost no mass and a negative charge.”

Page 13: Dr. Robert Barnard

Pursuasive DefinitionA Persuasive Definition is a definition designed

to produce a favorable or unfavorable emotional attitude toward whatever is denoted by the definiendum.

Persuasive definition relies upon both cognitive and emotive meaning. Since they exceed the scope of cognitive meaning, persuasive definitions are primarily rhetorical.

Page 14: Dr. Robert Barnard

Persuasive Definition ExamplesNeutral Definition:

Abortion: In medicine, an abortion is the premature exit of the products of conception (the fetus, fetal membranes, and placenta) from the uterus. It is the loss of a pregnancy and does not refer to why that pregnancy was lost.

Page 15: Dr. Robert Barnard

Unfavorable Emotive attitude definition:Abortion: The willful murder of innocent unborn

children, often performed to avoid the personal and societal consequences of wanton sexual activity.

Favorable Emotive attitude definition:Abortion: The constitutionally protected act of

medically resolving a pregnancy for the purpose of restoring, preserving or protecting the physical or mental health of a woman. The procedure is especially useful in protecting women from potentially debilitating consequences of rape and incest.

Page 16: Dr. Robert Barnard

Some Tools for Developing Definitions…

• Point to a case of the Definiendum (ostention)

• Specify the INTENSION of the term.• Enumerate (in part or whole) the

EXTENSION of the term.• Make the term precise by tracing its

place in a taxonomy.

Page 17: Dr. Robert Barnard

Ostensive (pointing) Definition

By “Dog” I mean:

By “Flux Capacitor” I mean:

Page 18: Dr. Robert Barnard

Definition by IntensionHere we indicate the characteristics or qualities

that the definiendum connotes.

Square: regular figure on a Euclidian plane bounded by four sides of equal length and four right angles.

Fish: cold-blooded, aquatic vertebrates, with gills, commonly fins, and often an elongated body covered with scales.

Page 19: Dr. Robert Barnard

Definition by Enumeration (extension)

Even numbers: 2, 4, 6, 8, 10, 12, 14, 16 …

Blue: the common feature of blueberries, the sky on a clear day, some people’s eyes, the ocean in some places, …

Page 20: Dr. Robert Barnard

Taxonomic Definition by Genus and Differentia

This sort of definition relies upon the fact that our concepts are often related by being more or less general. We have broad terms for general types and then other words for specific sub-types or case sunder the general heading.

• The GENUS is the general type• The DIFFERENTIA is the characteristic that marks a

specific sub-class or case.• A Genus and Differentia together define a SPECIES.

Page 21: Dr. Robert Barnard

Genus and Definition ExamplesTerm Genus DifferenceDAUGHTER = Offspring + FemalePUPPY = Dog + YoungSTUDENT = Person + Enrolled in

SchoolICE = Water + FrozenPRESIDENT = Political Leader + AmericanHOUSE = Structure + Free-standing ,

Permanent, Residential

SOCRATES = Human Being + Teacher of Plato

Page 22: Dr. Robert Barnard

Definitions and Meanings• Some terms have meaning which we record or

report with a lexical definition.• Some terms have more than one meaning, we

use precising definition to stipulate which meaning is relevant.

• Some terms are given meaning by a definition (ostensive, enumerative, theoretical)

• Some definitions contain emotive content that can be confused with cognitive content.

Page 23: Dr. Robert Barnard

Questions?

Page 24: Dr. Robert Barnard

NEW TOPIC: LOGICAL FORM

Page 25: Dr. Robert Barnard

Good vs. Bad Arguments• Deductive Validity – IF the premises are true

THEN the conclusion MUST be true.• Inductive Strength – IF the premises are true

THEN the conclusion WILL BE PROBABLE.• Deductive Soundness – the deductive

argument is valid AND premises are all true• Inductive Cogency—The inductive argument

is strong and the premises are all true

Page 26: Dr. Robert Barnard

Deduction and Argument Form• In order to talk about validity we need to

come back to the idea of an argument form.• Form is the STRUCTURE of the argument.• The Structure can either be good or bad. It

can either do its job or not.• A good structure will allow the premises to

support the conclusion.

Page 27: Dr. Robert Barnard

Review: Standard Form of an Argument

• Sample Argument: Socrates is mortal because all men are mortal

• Standard form isolates conclusion and lists ALL premises.

1) All men are mortal (given premise)2) Socrates is a man (implied premise)3) Socrates is mortal. (Conclusion)

Page 28: Dr. Robert Barnard

Logical Form of an Argument

• Determining Logical FORM:

If If Al likes SallyAl likes Sally then then Al will ask Sally outAl will ask Sally out

Al likes SallyAl likes Sally

Therefore Therefore Al will ask Al will ask Sally outSally out

If -- P -- then -- If -- P -- then -- Q--Q--

-- P –-- P –

Therefore -- Q --Therefore -- Q --

We Determine FORM by isolating the logical structure of the argument.

Page 29: Dr. Robert Barnard

Another example of logical form

[R] Every school teaches religion and religious beliefs. This can be seen by the fact that either a school is religious or not. And if it isn’t it either teaches a form of secular humanism or teaches atheism by teaching nothing. Both humanism and atheism therefore teach specific beliefs about religion.

Page 30: Dr. Robert Barnard

Isolate Conclusion FIRST

Every school teaches religion and religious beliefs. This can be seen by the fact that either a school is religious or not. And if it isn’t openly religious then it either teaches a form of secular humanism or teaches atheism by teaching nothing. Both humanism and atheism therefore teach specific beliefs about religion.

Page 31: Dr. Robert Barnard

LIST PREMISES

This can be seen by the fact that either a school is religious or not.

And if it isn’t openly religious then it either teaches a form of secular humanism or teaches atheism by teaching nothing.

Both humanism and atheism therefore teach specific beliefs about religion.

Every school teaches religion and religious beliefs.

Page 32: Dr. Robert Barnard

CLARIFY PREMISES1. Every school is openly Religious or not-openly

Religious. 2. If a school is not openly religious then it either

teaches secular humanism or teaches atheism by teaching nothing.

3. Both humanism and atheism are specific beliefs about religion.

SO… 4. Every school teaches religion and religious

beliefs.

Page 33: Dr. Robert Barnard

Add in an obvious assumed premise…

1. Every school is openly Religious or not-openly Religious. 2. All openly Religious schools teach religion and religious

beliefs3. Both humanism and atheism are specific beliefs about religion.

(re-ordered).4. If a school is not openly religious then it either teaches secular

humanism or teaches atheism by teaching nothing. SO…

5. Every school teaches religion and religious beliefs.

Page 34: Dr. Robert Barnard

SUBSTITUTE FOR TERMS

1. If S(chool) then R(eligious) or not-R. 2. If R, then T(eaches religion)3. If not-R then H (teach humanism) or A (teaches

atheism) (old 4 moved up)4. If H then T and If A then T

SO…

5. Every S is T

Page 35: Dr. Robert Barnard

Clarify

1. If S then (R or not-R). 2. If R, then T3. If not-R then (H or A) 4. (If H then T) and (If A then T)

SO…

5. If S then T (re-stated ‘if x then y’ = ‘all x are y’

Page 36: Dr. Robert Barnard

Issues !!!

• Is the form valid?• Is the analysis here correct? (Is Religious belief

the same as belief about religion?)• Are the premises true (soundness?)

Page 37: Dr. Robert Barnard

Validity and Form

KEY POINT:VALIDITY is a property of FORM

• If a given argument is valid, then ANY argument with the SAME FORM must also be VALID.

• Likewise: if a given argument is not valid, then ANY argument with the SAME FORM must also be INVALID.

Page 38: Dr. Robert Barnard

REMEMBER!!!!• Check on Homework

• Remember that the first QUIZ is due this week• Quiz PW is “fallacy”• Quiz is 1 take only!

• Quiz is open between T and R only!

• You have 200 minutes to complete 75 items.

Page 39: Dr. Robert Barnard