dr. robert barnard
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Philosophy 103Linguistics 103
Yet, still, Even further MoreIntroductory Logic:
Critical ThinkingDr. 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…
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
Plan for Today• Talk about Definitions• Time Permitting: Return to the issue of logical
form…
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
Types of Definitions
•Lexical•Precising•Theoretical•Persuasive
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.-
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!!!
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.
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.
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.”
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.
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.
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.
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.
Ostensive (pointing) Definition
By “Dog” I mean:
By “Flux Capacitor” I mean:
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.
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, …
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.
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
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.
Questions?
NEW TOPIC: LOGICAL FORM
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
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.
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)
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.
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.
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.
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.
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.
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.
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
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’
Issues !!!
• Is the form valid?• Is the analysis here correct? (Is Religious belief
the same as belief about religion?)• Are the premises true (soundness?)
Validity and FormKEY 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.
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.
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