TERM PREMISE Fallacies, Errors in Logic ARGUMENT
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9/10/2014 1 Fallacies, Errors in Logic Logical Arguments “If all terms in an argument are clear, and if all the premises in an argument are true, and if the argument is free from logical fallacy, then the conclusion must be true” A TERM is clear if it is intelligible and unambiguous A PREMISE is true if it corresponds to reality, if it says what it is. An ARGUMENT is logically valid if the conclusion follows from the premises and avoids any of the common logical pitfalls (fallacies) that we will study in class. What is a Fallacy? Fallacies are defects in an argument - other than false premises - which cause an argument to be invalid, unsound or weak. Informal Fallacies are the focus of this class Informal fallacies are defects which can be identified only through an analysis of the actual content of the argument rather than through its structure. Example of Informal Fallacy 1. Geological events produce rock. (premise) 2. Rock is a type of music. (premise) 3. Geological events produce music. (conclusion) a key term, "rock," is being used with two different definitions
Transcript of TERM PREMISE Fallacies, Errors in Logic ARGUMENT
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Fallacies, Errors in Logic
Logical Arguments
“If all terms in an argument are clear, and if all the premises in an argument are true, and if the argument is free from logical fallacy, then the conclusion must be true”
A TERM is clear if it is intelligible and unambiguous
A PREMISE is true if it corresponds to reality, if it says what it is.
An ARGUMENT is logically valid if the conclusion follows from the premises and avoids any of the common logical pitfalls (fallacies) that we will study in class.
What is a Fallacy?
Fallacies are defects in an argument - other than false premises - which cause an argument to be invalid, unsound or weak.
Informal Fallacies are the focus of this class
Informal fallacies are defects which can be identified only through an analysis of the actual content of the argument rather than through its structure.
Example of Informal Fallacy
1. Geological events produce rock. (premise) 2. Rock is a type of music. (premise) 3. Geological events produce music. (conclusion)
a key term, "rock," is being used with two different definitions
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False Dilemma
If we do not pass gun control laws now, we will never stop the rising number of murders in Chicago
Giving only two options when many exist
Ad Ignorantiam
Science cannot tell us about the outer limits of the universe so the universe must be infinite
Claim that a statement is true or false because it is unknown
Ad Baculum
If you do not comply with the distribution of certain healthcare procedures, there will be severe monetary
consequences
Appeal to force
Ad Misericordiam
Look at these poor mothers who are burdened with the care of so many children in sub-Saharan Africa, we
must promote population control
Appeal to pity
Ad Populum
Statistically most Americans are in favor of limiting the practice of Abortion, thus it should be limited
Appeal to majority
Ad Verecundiam
Dr. Smith has doctorates in medicine, law and physics and he says that the city should expand to outlying
areas. Thus, Nashville must develop better commute systems to and from the suburbs.
Appeal to fame or expertise
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Ad Hominem
You cannot listen to what she has to say, can’t you see what kind of life she is living!
Personal Attack
Hasty Generalization
Two adults have drowned in the last week off the coast of Finland. We must mandate swimming lessons for all adults because clearly they do not know how to
swim
Considering only exceptional cases
False Analogy
The Church cannot tell me what I should do in my personal life, just like the government cannot tell me
what color shoes to wear!
Comparisons which seem similar but are actually different
Post hoc, ergo propter hoc
Just after a cold spell came through I developed an earache. The change in temperature caused my
earache.
After this therefore because of this
Begging the Question
Nike is the most quality basketball shoe on the market – just look at how quality they are!
Failing to back up a claim
Circular Reasoning
For greater financial stability you need to have a larger savings account, because the more you have in savings
the more you are financially secure.
Assuming what you are arguing for
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Straw Man
A small tax cut should be made for small-business owners.
A tax cut! How can we afford billions of dollars of lost revenue to selfish and greedy business owners who do
not even care for the needs of their own employees.
Distorting the opponents position
Composition/Division
Composition: This iPhone malfunctions regularly. All iPhones are junk.
Division: The Ford Mustang won this year’s top prize
for design quality. Its engine is the best designed engine in the world.
Drawing false conclusions from a whole or it’s parts
Non Sequitur
Affirming the Consequent: If it rains, the ground gets wet. The ground is wet, therefore it rained. (If A then
B, B, therefore A)
Denying the Antecedent: If it rains, the ground gets wet. It is not raining, therefore the ground is not wet.
(If A then B, Not A, thus not B)
Conclusion does not follow from the premises
