Download - Logic, Debate, and Reasoning
![Page 1: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/1.jpg)
LOGIC, DEBATE, AND REASONINGPresented by Ratio Christi TAMU
![Page 2: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/2.jpg)
WHAT IS LOGIC The science of analyzing arguments?
The science of good reasoning in general?
Tagore A mind all logic is like a knife all blade, it
makes the hand bleed that uses it
![Page 3: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/3.jpg)
WHAT IS A FORMAL ARGUMENT Premises that lead to a conclusion
P1: If God exists he works all events for the good of those who believe;
P2: Some events produce no good; C: Therefore God does not exist.
The conclusion either follows from the premises logically, or is at least probable given the premises.
√
![Page 4: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/4.jpg)
ROADMAPTypes of Arguments• Inductive• Deductive
Bad Arguments• Formal Fallacies• Informal Fallacies
Tactics• Analysis
![Page 5: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/5.jpg)
TYPES OF ARGUMENTS Inductive
Results in a high probability that the conclusion is true.
Common in science
Deductive Arguments If the premises are true,
and the structure is correct, the conclusion must be true.
![Page 6: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/6.jpg)
INDUCTIVE ARGUMENTS Has premises and conclusion, but is
probabilistic 100% of biological life forms that we know of
depend on liquid water to exist. Therefore, if we discover a new biological life form
it will probably depend on liquid water to exist. Used in the scientific method The conclusion is not certain, only
probable
![Page 7: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/7.jpg)
STATISTICAL SYLLOGISM Statistical Syllogism
P1: Most Greeks ate fish; P2: Socrates was a Greek; C: Therefore Socrates probably ate fish.
Similar in form to the deductive syllogism The conclusion is still not certain,
only probable
![Page 8: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/8.jpg)
GENERALIZATION Assumes a sample has
the same attributes as a population
10% of the survey were Democrats
Therefore, 10% of people are Democrats
![Page 9: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/9.jpg)
ANALOGY Compares two situations
Situations A and B are similar in properties X and Y
Situation A also has property Z Therefore, B probably has property Z as
well
May provide good evidence for a claim Is not conclusive
![Page 10: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/10.jpg)
PREDICTION Draws a conclusion about the future
from the past Every time in the past that an apple has
been dropped, it has fallen. Therefore, if I drop an apple now, it will
probably fall
One of the foundational assumptions of science
![Page 11: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/11.jpg)
DEDUCTIVE ARGUMENTS Has premises and conclusion
P1: All men are mortal; P2: Socrates was a man; C: Therefore Socrates was mortal.
The conclusion is certain, but only if the premises are true and the structure is correct
√
![Page 12: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/12.jpg)
VALIDITY AND SOUNDNESS Validity
An argument is valid if it has the correct form
Sound An argument is sound if it is valid
and the premises are true
![Page 13: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/13.jpg)
TYPES OF DEDUCTIVE REASONING Categorical Logic Propositional Logic Modal Logic
![Page 14: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/14.jpg)
CATEGORICAL LOGIC First formalized by Aristotle Made up of simple statements Not all arguments can be translated
into this form But many can be translated into this form
![Page 15: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/15.jpg)
CATEGORICAL LOGIC 4 types of statements
All S are P No S are P Some S are P Some S are not P
Can be combined into groups of three called a syllogism
![Page 16: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/16.jpg)
CATEGORICAL SYLLOGISM Requires two kinds of premises
Major Premise: All men are mortal; Minor Premise: Socrates was a man; Conclusion: Therefore Socrates was
mortal. The premises must share a term
(middle term) P1: All men are mortal; P2: Socrates was a man; C: Therefore Socrates was mortal.
![Page 17: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/17.jpg)
CATEGORICAL SYLLOGISMS Not all combinations of terms are valid;
P1: All cats are mammals; P2: Oreo is a Cat; C: Therefore Oreo is a mammal.
P1: All mammals are animals; P2: some cats are animals; C: Therefore some cats are mammals.
X
√
![Page 18: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/18.jpg)
PROPOSITIONAL LOGIC The most basic logic dealing with conditionals If then statements, etc.
More powerful than simple categorical syllogisms 9 basic rules
![Page 19: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/19.jpg)
RULE #1 MODUS PONENS
If P, then Q P Therefore, Q
Valid, example: If the ground is wet, it is raining The ground is wet Therefore it is raining
(this one is unsound because the premise is false)
√
![Page 20: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/20.jpg)
RULE #2 MODUS TOLLENS
If P, then Q Not Q Therefore, not P
Valid, example: If it is raining, the ground is wet The ground is not wet Therefore it is not raining
(This one may be unsound as well)
√
![Page 21: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/21.jpg)
RULE #3 HYPOTHETICAL SYLLOGISM If P then Q If Q then R Therefore if P then R
Example If it is raining, the ground is wet If the ground is wet, the roads are slippery Therefore, if it is raining, the roads are
slippery√
![Page 22: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/22.jpg)
RULE #4 CONJUNCTION P Q Therefore P and Q
Example John is a good student Mary is a good student Therefore John is a good student and Mary
is a good student√
![Page 23: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/23.jpg)
RULE #5 SIMPLIFICATION P and Q Therefore P
Example John is a good student and Mary is a good
student Therefore John is a good student
√
![Page 24: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/24.jpg)
RULE #6 ABSORPTION If P then Q Therefore If P then P and Q
Example If it is raining, the road is wet Therefore if it is raining, it is raining and
the road is wet√
![Page 25: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/25.jpg)
RULE #7 ADDITION P Therefore P or Q
Example It is raining Therefore if it is raining or the sun is
shining√
![Page 26: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/26.jpg)
RULE #8 DISJUNCTIVE SYLLOGISM P or Q Not P Therefore, Q
Example It is either raining or the sun is shining It is not raining Therefore, the sun is shining√
![Page 27: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/27.jpg)
RULE #9 CONSTRUCTIVE DILEMMA If P then Q and If R then S P or R Therefore, Q or S
Example If it is raining the streets are wet, and if it
is sunny the streets are dry It is either raining or sunny Therefore, the streets are wet or the
streets are dry
√
![Page 28: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/28.jpg)
EXAMPLE If God exists and the present moment is real, then
God is in time If God is in time, then he knows what is happening
now If God knows what is happening now, then now exists Either now does not exist, or Einstein's theory is
wrong The present moment is real Therefore if God exists, Then Einstein’s theory is
wrong (However this may be unsound)√
![Page 29: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/29.jpg)
ROADMAPTypes of Arguments• Inductive• Deductive
Bad Arguments• Formal Fallacies• Informal Fallacies
Tactics• Analysis
![Page 30: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/30.jpg)
FORMAL FALLACIES Result from errors of logical form
May have true conclusions But the conclusion does not follow from the
premises
![Page 31: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/31.jpg)
INCORRECT CATEGORICAL SYLLOGISM Many types: Ex:
All communists are leftists. No conservatives are communists. Therefore, no conservatives are leftists.
Ex: All dogs are animals. No cats are dogs. Therefore, no cats are animals.
X
X
![Page 32: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/32.jpg)
AFFIRMING THE CONSEQUENT Improper modus ponens Ex:
If God exists, then objective morals and duties exist
Objective morals and duties do exist Therefore God exists
X
![Page 33: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/33.jpg)
DENYING THE ANTECEDANT Improper modus tollens Ex:
If God does not exist then objective values and duties do not exist
God does exist Therefore objective values and duties exist
X
![Page 34: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/34.jpg)
INFORMAL FALLACIES Mistakes in reasoning that arise from
the content of the argument⁻ Ad hominem⁻ Red herring ⁻ Straw man⁻ Appeal to Authority⁻ Slippery Slope⁻ Weak Analogy⁻ Hasty Generalization
⁻ False Cause⁻ Appeal to
Ignorance⁻ Bandwagon⁻ Genetic Fallacy⁻ Begging the question
⁻ Appeal to Emotion⁻ Special pleading⁻ Equivocation⁻ Self refuting Statements
![Page 35: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/35.jpg)
Meaning: “To the man” Favorite of politicians Ex:
"All politicians are liars, and you're just another politician. Therefore, you're a liar and your arguments are not to be trusted."
AD HOMINEM
X
![Page 36: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/36.jpg)
An irrelevant fact intended to divert attention from the real issue
Therefore, if morality exists, then God must exist too!
Sure, but what about slavery in the Bible? That does not sound very moral to me…
Don’t take the bait!
RED HERRING
X
![Page 37: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/37.jpg)
Misrepresenting your opponents position so it can be more easily defeated
“Here is the message that an imaginary 'intelligent design theorist‘ might broadcast to scientists: 'If you don't understand how something works, never mind: just give up and say God did it.” –Richard Dawkins
“one of the truly bad effects of religion is that it teaches us that it is a virtue to be satisfied with not understanding.” -Richard Dawkins
STRAW MAN
X
X
![Page 38: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/38.jpg)
APPEAL TO ILLEGITIMATE AUTHORITY If an argument is based on authority, it
should be a legitimate authority, otherwise it is a bad argument
Ex: Biogeography gives very strong evidence for evolution. But Ray Comfort says evolution is false!
X
![Page 39: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/39.jpg)
SLIPPERY SLOPE Argues that by permitting A to occur, a
far-fetched Z will occur. Only fallacious if Z is not a likely
consequence of A Ex:
Colin Closet asserts that if we allow same-sex couples to marry, then the next thing we know we'll be allowing people to marry their parents, their cars and even monkeys. –yourlogicalfallacy.com
X
![Page 40: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/40.jpg)
WEAK ANALOGY If using an inductive analogy, the
analogy must be strong or the argument is fallacious
Ex: Cars and motor-boats both have engines and steering wheels. Cars have wheels Therefore boats must have wheels as well
X
![Page 41: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/41.jpg)
HASTY GENERALIZATION Drawing a conclusion about a whole
group based on a few members of that group Not all generalizations are hasty
Ex: Both of the politicians I have met were liars Therefore, all politicians are liars
X
![Page 42: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/42.jpg)
FALSE CAUSE Post hoc ergo proctor hoc (After
this therefore because of this) Correlation does not imply causation
Ex: Pointing to a fancy chart, Roger shows
how temperatures have been rising over the past few centuries, whilst at the same time the numbers of pirates have been decreasing; thus pirates cool the world and global warming is a hoax.
–yourlogicalfallacy.com
X
![Page 43: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/43.jpg)
APPEAL TO IGNORANCE Draws a conclusion from a lack of
evidence Absence of evidence is not necessarily
evidence of absence
Ex: You arguments have failed to show that God
exists; Therefore, God must not exist.
X
![Page 44: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/44.jpg)
BANDWAGON Everyone knows that…
Ex: Everyone knows that Stephen Hawking disproved
God…X
![Page 45: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/45.jpg)
GENETIC FALLACY Claiming a belief is false because you can
explain why someone believes it “Why aren’t you a Hindu? Because you happen
to have been brought up in America, not in India. If you had been brought up in India, you’d be a Hindu. If you’d been brought up in Denmark at the time of the vikings, you’d be believing in Wotan and Thor. If you had been brought up in classical Greece you’d be believing in Zeus. if you had been brought up in central Africa, you’d be believing in the great Juju up the mountain.” –Richard Dawkins
X
![Page 46: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/46.jpg)
BEGGING THE QUESTION How do I know the Bible is true?
Because the Bible says it is true, and I believe it!X
![Page 47: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/47.jpg)
Argument from Emotion An appeal to
emotion “they were
religious, and that provided all the justification they needed to murder and destroy” –Richard Dawkins
“Imagine, with John Lennon, a world with no religion. Imagine no suicide bombers, no 9/11, no 7/7, no Crusades, no witch-hunts…” –Richard Dawkins
X
![Page 48: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/48.jpg)
SPECIAL PLEADING Exempting your claims from your own
requirements Everything that exists has a cause God exists So what caused God? A: God doesn’t count because He’s uncaused!
X
![Page 49: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/49.jpg)
EQUIVOCATION Using the same word with two different
meanings Define your terms!
![Page 50: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/50.jpg)
SELF REFUTING STATEMENTS The argument
proves itself to be wrong
![Page 51: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/51.jpg)
ROADMAPTypes of Arguments• Inductive• Deductive
Bad Arguments• Formal Fallacies• Informal Fallacies
Tactics• Analysis
![Page 52: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/52.jpg)
ANALYZING ARGUMENTS Arguments are rarely stated in simple
syllogisms We must take complex arguments and
break them down into simple parts we can analyze
![Page 53: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/53.jpg)
EXAMPLE 1 What would happen if we get down on our
knees and pray to God in this way: Dear God, almighty, all-powerful, all-loving
creator of the universe, we pray to you to cure every case of cancer on this planet tonight. We pray in faith, knowing you will bless us as you describe in the Bible. In Jesus' name we pray, Amen.
We pray sincerely, will anything happen? No. Of course not
http://godisimaginary.com/i1.htm
![Page 54: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/54.jpg)
ANALYSIS What was the argument Maybe…
God promises to answer all prayers God didn’t give me what I prayed for Therefore God does not exist
![Page 55: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/55.jpg)
ANALYSIS False premise
God promises to answer all prayers
Christians do not necessarily believe this, so the argument is unsound
![Page 56: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/56.jpg)
ANALYSIS What was the argument?
If I pray and God exists, then God will answer my prayer
I prayed God didn’t answer my prayer Therefore God does not exist
This is valid, but Christians may disagree with the premises
![Page 57: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/57.jpg)
EXAMPLE 2“We could learn to live with people from all races and not immediately hating and wanting to kill someone just because they believe in a different god.Yes, a world without God would be a far better, friendlier and happier place. A world without religion would also be a safer place for innocent children, who have been abused by the religious-lot for centuries and continue to be abused.” –god-does-not-exist.org
![Page 58: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/58.jpg)
ANALYSIS This argument was an argument from
emotion It did not provide facts or evidence It only claimed that religion harms
children
![Page 59: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/59.jpg)
EXAMPLE 3 To understand why "God does not exist" can be a legitimate
scientific statement, it's important to understand what the statement means in the context of science. When a scientist says "God does not exist," they mean something similar to when they say "aether does not exist," "psychic powers do not exist," or "life does not exist on the moon."
All such statements are casual short-hand for a more elaborate and technical statement: "this alleged entity has no place in any scientific equations, plays no role in any scientific explanations, cannot be used to predict any events, does not describe any thing or force that has yet been detected, and there are no models of the universe in which its presence is either required, productive, or useful."
![Page 60: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/60.jpg)
ANALYSIS What is the argument:
There is no empirical evidence that can only be attributed to God
If God exists, then he will produce empirical evidence
Therefore God does not exist.
![Page 61: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/61.jpg)
ANALYSIS What is the argument:
There is no empirical evidence that can only be attributed to God
If God exists, then he will produce empirical evidence
Therefore God does not exist. This is deductively valid (maybe) But is it True?
√
![Page 62: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/62.jpg)
ANALYSIS There is no empirical evidence that can
only be attributed to God If God exists, then he will produce
empirical evidence Therefore God does not exist.
We would disagree with the first premise, and maybe even the second premise!
XX
![Page 63: Logic, Debate, and Reasoning](https://reader036.vdocument.in/reader036/viewer/2022062410/56815c48550346895dca4906/html5/thumbnails/63.jpg)
CONCLUSION Logic can be a useful tool in
understanding arguments But arguments are rarely in logical form Therefore, it is useful to be able to
analyze arguments in logical form to find errors