logic_ chapter #1 by mian waqas haider.pptx

8/10/2019 Logic_ Chapter #1 by Mian Waqas Haider.pptx

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Introduction to LogiMian Waqas Haider


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CHAPTER# 1


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MAN VS. AN

Unexamined Lworth living


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L D


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LOGIC: DEFINITIONSFROMDIFFER

ANGLES.Logic is a Science of Reasoning.

Logic is the study of the valid princiused to distinguish correct reasoning

incorrect reasoning.

Logic is an organized body of knowscience that evaluates arguments who

is to provide standards for determinin

truth of validity and thought.


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DEFINITIONOFLOGIC


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HISTORYOFLOGIC


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SUBJECTMATTEROFLOG


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REPEATEDQUESTIONINC

What benefits are to be achiev

from the study of logic? Discus

2000OR why should we study Logic? Discu

importance in everyday life.


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OBJECTIVES AND BENEFITS


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OBJECTIVESANDBENEFITS

LOGIC


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LOGICTEACHESUS

To reason correctly

To evaluate or test arguments of the other

To construct our owns arguments

To develop methods and techniques to

distinguish good argument from bad argum

WHY TO STUDY LOGIC? OR


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WHYTOSTUDYLOGIC? OR

BENEFITSOFLOGIC


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IMPORTANTLY,

Logic is "therapeutic": we learn logrecognize and to construct good argum

Formal logic is an indispensable itemcontemporary philosopher's toolkit.

It develops thinking abilities systemat


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ARISTOTLESLOGIC

He says Logic studies thought Thought means not process but pro

thought

1. Concept (Term)2. Judgment (Proposition)

3. Inference (argument)


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CONCEPT

Property of mindPicture of a thing in mind

A mental image

E.g., table, chair, pen, book


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TERM

Concept expressed in language

Categorematic: term by itself; man, t

Syncategorematic: not term by themsthe, an, all, only, of

Acategorematic: used in neither case

hurrah! Alas


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TERM

Positive termNegative term

private


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TERMS

Positive: table, chair, manNegative: not-table, not-chair

Private: blind, deaf, dumb


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SINGULARANDGENERALTE

Particular term, Socrates, Ravi, Laho

Universal terms, man, cricket, univers


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JUDGMENT

Relationship of affirmation/negation bconcepts.

Intellectual activity

Comparison/ evaluation of particular of an experience

Psychological activity of awareness o

objects and relationships


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PROPOSITION

Judgment expressed in language

True or false statement

Witten or spoken statement in langua

3 parts:Subject

Predicate

copula


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A logical sentence.

It consists of terms (subject & Predica

Subject and predicate are two classe

which are related or linked through coExample of Proposition:

Subject copula Pred

All Men are Mo

PROPOSITION

P


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PROPOSITION


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I


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INFERENCE

Combination of more than 1 propositi

Mental activity

Where some propositions are given

(premises) , and other follow from the

(conclusion).

I


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INFERENCE

A inference or reasoning is a process o

transition from known/perceived facts (Pto unknown or unperceived reasoning.

You see smoke and infer/ reason that tfire.

I


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INFERENCE

REASONING


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REASONING


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All Men are Mortal.

Socrates is a Man.

Therefore, Socrates is Mortal.

Premis

C


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ARGUMENT


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ARGUMENT


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PREMISES


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PREMISES

PREMISES INDICATORS


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PREMISESINDICATORS

CONCLUSION INDICATOR


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CONCLUSIONINDICATOR

TWO TYPES OF ARGUMENT


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TWOTYPESOFARGUMENT

Formal Argument

Informal argument

FORMALARGUMENT


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Formal Argument deals with1. form/ structure of argument. For example:

All M are P All Scientists are Researchers. All S are M All Professors are scientists. All S are P Therefore, All Professors are resea

OR 2 + 2 = 4

2. Arrangement of terms and forms of proposition in an a

3. Constructed systems of logic carrying proofs.4. Notion of form refers to norms/rules/laws of expressio

Normative Science)5. Our thoughts are also formal n structured.6. Language and rules of reasoning are precisely carefulDeduct ive reason ingsyl log isms, mathemat ics and com

INFORMAL ARGUMENT


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INFORMALARGUMENT

Deals with content (meaning) of argu

Study of reasoning and fallacies in th

context of everyday language and life

FORMALARGUMENTAND


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INFORMALARGUMENT

Difference b/w Deductive reasoning (

formal argument) and Inductive reaso

(an informal argument)


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DEDUCTIVE REASONING


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DEDUCTIVEREASONING

1. In deductive argument, we move f r

universal(general info) to part icu lar

(specific observation).

Example:

All men are mortal. (universal)

Socrates is a man.

Therefore, Socrates is mortal (particu

2 Conclusion follows necessari ly


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2. Conclusion follows necessari ly

premises.

3. If premises are true, then concl

must be true.

4. In deductive reasoning, relation

b/w premises and conclusion is of

Certainty or must be


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DEDUCTIVE ARGUMENT


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DEDUCTIVEARGUMENT

5. DEDUCTIVEREASONINGIS


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TOP-DOWNAPPROACH

Because it moves from top (universa

greater) to down (Particular or smaller

All men are mortal. (top) Universal

Socrates is a man.

Socrates is mortal. (down) Particular

TOP-DOWN APPROACH


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TOP DOWNAPPROACHEvery person has a head. (start her

Conclusion:

Aslam is a person.

Therefore Aslam has one h

TOP-DOWN APPROACH


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TOP DOWNAPPROACH

6. DEDUCTIONISUSEDTOTE


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HYPOTHESISANDTHEORIESE

7. DEDUCTIVEREASONINGISTH


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WHICHARGUERCLAIMSTHAT

IMPOSSIBLEFORTHECONCLUSIBEFALSEGIVENTHATPREMISES

TRUE.

8. Mathematical arguments , catego

dis junct ive and hypo thet ica l sy l log

are examples o f deduct ive reasonin

INDUCTIVEREASONING


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1. It moves from part icu lar observa

to universal truth .

Crow 1 is black

Crow 2 is black Particular facts

Crow 3 is black

Therefore, all crows are black. (unive

INDUCTIVEREASONING


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2. In this argument, conc lusion is p robabl

fo l low s from premises.

3. If prem ise are true, then conclusion is u

or improbable" to be false.

4. The relat ionship b /w p remises and con

is o f probabi l i ty .

6. INDUCTIVEREASONINGISTO MAKE HYPOTHESIS LAWS


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TOMAKEHYPOTHESIS, LAWS

THEORIES


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7. INDUCTIVEREASONINGISABO

UP APPROACH


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UPAPPROACH.

BOTTOM-UPAPPROACH


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Man 1 has only 1 head. Man 2 has only 1 head. Man 3 has only

Every man has 1 head.


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Deductive VS. Inductivereasoning


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reasoning1. Premises provide

conclusive grounds forconclusion.

2. Relationship b/w

premises and conclusionis CERTAIN.

3. Valid or invalid

1. Premises prov

some support forconclusion.

2. Relationship b

premises and conis PROBABLE.

3. Strong or wea

Deductive VS. Inductivereasoning


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reasoning4. Truth preserving

5. Not based on sense-experience

6. Conclusion necessarily

follows from premises

7. Mathematics is based ondeductive reasoning

4. Not truth preserv

5. Based on senseexperience

6. Conclusion prob

follows from premise

7. Natural scienceson inductive reasonin

SUMMARYARGUMENTS


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Deductive Inductive

Begins from known statement Begins from unknown s

Universal to particular Particular to unive

Necessary support Probable support

Valid Invalid Strong weak

Can be proved on logical grounds cannot be proved on logica

TRUTH, VALIDITY, SOUNDNESSTRENGTH COGENCY


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STRENGTH, COGENCYTruths property of statement/proposi

Validity (valid/invalid) and soundness

characteristics of deductive argument

Strength (weak/strong argument) and

cogency are characteristics of inductiv

argument.

TRUTH, VALIDITY, SOUNDNESS, STREN

COGENCY


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COGENCYTruth and Falsity Proposition

Validity & InvaliditySoundness & unsoundness

Strength & weaknessCogency & Uncogency

Deductive

argument

Inductive

argument

TRUTH


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Truth and falsity are the characterist

propositions.1. Material Truth: proposition should

according to facts. Its changeable. Truth

present in external world.2. Formal Truth:its not conditional a

depends up its own nature. Unchangeab

l i l iti

VALIDITY


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Validity and invalidity are characteristics o

deductive arguments

Conclusion should necessarily follow from

premises.

It is formal aspect of thought.

Validity depends upon truth of premises aconclusion.

Argument must be invalid, if all premises a

and conclusion is false.

VALIDITY


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SOUNDNESS


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Two conditions must be met.

1. A rgument must be valid .

2. A l l its prem ises mus t be true.

Soundness= All True Premises +

Argument

SOUNDARGUMENTIf deductive argument is val id and ha


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If deductive argument is val id and ha

prem ises true,then it is called sound

argument.Sound Argument= Valid Argument+ A

True Premises

All men are mortalSocrates is a man.

Therefore, Socrates is mortal.

UNSOUNDARGUMENT


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Inval id argument w ith all (or one o

premises being false is unsoundargument.

All monkeys eats mangoes.Mr. x eats mangoes

Therefore, Mr. x is a monkey.


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STRONGARGUMENT


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It is a inductive argument in which

conclusion strongly follows from premit is improbable for conclusion to be fa

given that premises are true.

In weak inductive argument, conclus

probably follows from premises.


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CATEGORICALSYLLOGISM

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