OJV1 Lesson 6

ILS1: Introduction to Textual Analysis 6

INTRODUCING TEXTUAL LOGIC November 9, 2018

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Definition 

Logic is a formal system of analysis that helps to “invent”, demonstrate, and prove arguments in a text.

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It works by testing propositions (i.e. statements, claims, sentences) against one another to determine their accuracy.

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What is Logical? 

We often think that we are using logic if we avoid emotion or if we make arguments based on common sense, such as  "Everyone should look out for their own self interests" or  "People have the right to be free."

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However, unemotional or common sense statements are not always equivalent to logical statements (!)

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Basic Vocabulary Premise: Proposition used as evidence in an argument.

Argument: The assertion of a conclusion based on logical premises.

Conclusion: Logical result of the relationship between the premises.

Syllogism: The simplest sequence of logical premises and conclusions (first devised by Aristotle).

Induction: A process through which the premises provide initial basis for the conclusion.

Deduction: A process through which the premises provide conclusive proof for the conclusion.

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Syllogisam ď Ž

The most famous logical sequence, called the syllogism, was developed by the Greek philosopher Aristotle. His most famous syllogism is:

ď Ž

Premise 1: All men are mortal.

Premise 2: Socrates is a man.

Conclusion: Therefore, Socrates is mortal.

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Commentary ď Ž

In this sequence, premise 2 is tested against premise 1 to reach the logical conclusion.

ď Ž

Within this system, if both premises are considered valid, there is no other logical conclusion than determining that Socrates is mortal.

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Reaching Logical Conclusions Example A: Consider the following premises: Premise 1: Non-renewable resources do not exist in infinite supply.

Premise 2: Coal is a non-renewable resource.

From these two premises, only one logical conclusion is available: Conclusion: Coal does not exist in infinite supply.

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ď Ž

Example B: Often logic requires several premises to reach a conclusion.

Premise 1: All monkeys are primates.

Premise 2: All primates are mammals.

Premise 3: All mammals are vertebrate animals.

Conclusion: Monkeys are vertebrate animals.

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Example C: Notice that logic requires decisive statements in order to work. Therefore, this syllogism is false: Premise 1: Some quadrilaterals are squares.

Premise 2: Figure 1 is a quadrilateral.

Conclusion: Figure 1 is a square.

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Commentary This syllogism is false because not enough information is provided to allow a verifiable conclusion.

Figure 1 could just as likely be a rectangle, which is also a quadrilateral.

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Example D: Logic can also mislead when it is based on false premises that an audience does not accept. For instance: Premise 1: People with red hair are not good at checkers.

Premise 2: Bill has red hair.

Conclusion: Bill is not good at checkers.

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Commentary Within the syllogism, the conclusion is logically valid.

However, it is only true if an audience accepts Premise 1, which is very unlikely.

This is an example of how logical statements can appear accurate while being completely false.

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Example E: For instance, these two syllogisms about the platypus reveal the limits of logic for handling ambiguous cases: Premise 1: All birds lay eggs.

Premise 2: Platypuses lay eggs.

Conclusion: Platypuses are birds.

Premise 1: All mammals have fur.

Premise 2: Platypuses have fur.

Conclusion: Platypuses are mammals.

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Commentary Logical conclusions also depend on which factors are recognized and ignored by the premises.

Therefore, different premises could lead to very different (both true and false) conclusions about the same subject.

Though logic is a very powerful argumentative tool and is far preferable to a disorganized argument, it does have its limits.

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Logical Fallacy Logical Fallacies are common errors in reasoning. ď Ž They will undermine the logic of your argument. ď Ž Fallacies can be either illegitimate arguments or irrelevant points, and are often identified because they lack evidence that supports their claim. ď Ž

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Slippery Slope: 

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This is a conclusion based on the premise that if A happens, then eventually through a series of small steps, through B, C,..., X, Y, Z will happen, too, basically equating A and Z. So, if we don't want Z to occur, A must not be allowed to occur either.

Example:  If we allow the children to choose the movie this time, they are going to expect to be able to choose the school they go to or the doctors they visit.  All types of murder will become legal if we legalize voluntary active euthanasia.

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Hasty Generalization: 

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This is a conclusion based on insufficient or biased evidence. In other words, you are rushing to a conclusion before you have all the relevant facts. Also, drawing a conclusion based on a small sample size, rather than looking at statistics that are much more in line with the typical or average situation.

Example:  Five congressional representatives have had affairs.

Therefore, members of Congress are adulterers.  I've met three redheads and they were all mean, so all redheads are mean

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Post hoc ergo propter hoc: This is a conclusion that assumes that if 'A' occurred after 'B‘, then 'B' must have been caused by 'A.'  Example: 

I

drank bottled water and now I am sick, so the water must have made me sick.  We raised the tax rate and crime went down, so the tax rate caused crime to go down.

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Genetic Fallacy: 

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This conclusion is based on an argument that the origins of a person, idea, institute, or theory determine its character, nature, or worth.

Example:  The Volkswagen Beetle is an evil car because it was originally designed by Hitler's army.  That is not possible because he got the idea from a science fiction film.

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Begging the Claim (or Circular Argument): 

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In this case, the conclusion that the writer should prove is validated within the claim. Or, it is any form of argument where the conclusion is assumed in one of the premises.

Example:  Filthy and polluting coal should be banned.  God exists because the Bible says so, and the Bible is true because it is the word of God.

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Either/or (or Black and White Thinking): This is a conclusion that oversimplifies the argument by reducing it to only two sides or choices.  Example: 

 We

can either stop using cars or destroy the Earth.  You must be a Republican or Democrat. You are not a Democrat. Therefore, you must be a Republican.

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Ad hominem:  

This is an attack on the character of a person rather than his or her opinions or arguments.

Example:  Green Peace's strategies aren't effective because they are all dirty, lazy hippies.  My opponent suggests that lowering taxes will be a good idea -- this is coming from a woman who eats a pint of Ben and Jerry’s each night!

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Ad populum (Bandwagon): 

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This is an emotional appeal that speaks to positive (such as patriotism, religion, democracy, intelligence) or negative (such as terrorism or fascism) concepts rather than the real issue at hand. Also, it promotes an assumption that something is good just because everyone else is doing it: when it is argued that a conclusion must be true because most people believe it is true.

Example:  Only very intelligent people like you are smart enough to know God exists.  Eating animals is moral because we have been eating them for thousands of years 24 24

Red Herring: 

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This is a diversionary tactic that avoids the key issues, often by avoiding opposing arguments rather than addressing them.

Example:  The level of mercury in seafood may be unsafe, but what will fishers do to support their families?  Bob: You really shouldn’t charge them 30% on their loans. It’s unethical.

Dan: Well, someone else would charge that rate if I didn’t.

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Absolutism  

Absolutism arises when we make no exceptions for the rules that do have exceptions.

Example:  Bob

believes you should never lie. So, he tells the Nazis where the Jews are hidden.  Pete believes hard work leads to flourishing.

Therefore, Pete thinks that starving children in Africa simply do not work hard.

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Relativism 

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The relativist fallacy arises when we illegitimately argue that nobody is incorrect because what is true for you is false for me, and we are both correct. Relativism is based on the idea that each culture or person creates their own truth, so nobody is objectively incorrect.

Example:  “The earth is flat” is true for me and false for you. So, respect my opinion.

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Moral Equivalence: (also called False equivalence) is often used in political debates. ď Ž It seeks to draw comparisons between different, even unrelated things, to make a point that one is just as bad as the other or just as good as the other. ď Ž

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Moral Equivalence Example ď Ž

A common manifestation of this fallacy is a claim, often made for ideological motives, that both sides are equally to blame for a war or other international conflict. Historical analyses show that this is rarely the case. Wars are usually started by one side militarily attacking the other, or mass murdering with or without provocation from the other side.

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Straw Man ď Ž

Arguing against an opponent by misrepresenting the opponent’s position. It occurs when someone argues that a person holds a view that is actually not what the other person believes. Instead, it is a distorted version of what the person believes.

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Straw Man (Example) Pete: What is your view on the Christian God? Mike: I don’t believe in any gods, including the Christian one.

Pete: So you think that we are here by accident, and all this design in nature is pure chance, and the universe just created itself?

Mike: You got all that from me stating that I just don’t believe in any gods?

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Burden of Proof “I can’t prove that my claim is true, but you must prove it is false.” (also known as petition principii).  Example: 

 Lisa

believes in ghosts. Mark tells her that there is no evidence that ghosts exist. Lisa tells Mark that there is no evidence that they don't.

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Cherry Picking 

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Cherry picking is when we look only for confirming evidence for our ideas. We ignore, suppress, do not see, or do not test for disconfirming evidence for our ideas.

Example:  My

political candidate gives 10% of his income to the needy, goes to church every Sunday, and volunteers one day a week at a homeless shelter. Therefore, he is honest and morally straight.

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Non sequitur 

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When the conclusion does not follow from the premises.

In more informal reasoning, it can be when what is presented as evidence or reason is irrelevant or adds very little support to the conclusion.

Example:  People generally like to walk on the beach. Beaches have sand. Therefore, having sand floors in homes would be a great idea!  Slim, of medium height, and with sharp features, Mr. Smith's technical skills are combined with strong leadership qualities.

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