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PHIL 201 : EXAM 2
Laws of Logic |
The foundation of all reasoning. If they're not accepted as true, then nothing we say or reason makes any sense. These laws are undeniable. |
Law of Non-contradiction (Laws of Logic) |
Something cannot both be & not be at the same time and in the same respect ~(P&~P) |
Law of Excluded Middle (Laws of Logic) |
Something either is or is not. Pv~P |
Law of Identity (Laws of Logic) |
Something is what it is. P=P |
Undeniable |
laws cannot be meaningfully denied. Any person using these laws has to use them as the basis for denial. (Hence a denial would be self-defeating: she would be defeating the very point she is trying to make.) |
premises |
reasons |
Conclusion |
belief that one is trying to support |
Inference |
the relationship between the premises and the conclusion |
Validity |
Refers-to the structure of an argument; an argument is considered valid if the conclusion follows from the premises; it is invalid if the conclusion does not follow (non-sequitur)
"I have a blue car.
Gravity is a good movie.
Therefore, I love pizza." |
Truth Value |
Refers to the quality of the propositions in the argument; arguments are valid or invalid but propositions are true or false. |
Sound |
An argument is sound if it is both valid & the premises are true; an argument may be valid and unsound but can never be invalid and sound; an argument is unsound if it is either invalid or one or more of the premises are false. |
Deduction |
a form of logical reasoning in which the aim is to arrive at a conclusion that is logically necessary given the premises. |
Syllogism |
Formal procedure for writing out a deductive argument.
Made up of categorical propositions. |
Categorical Proposition |
A proposition that affirms or denies something in terms of two categories: subject & predicate. |
Disjunctive Proposition |
A proposition which affirms or denies something in terms of two alternatives (known as alternant) in the form of an "either/or" statement. |
Alternant |
A disjunctive proposition is an either/or statement that affirms or denies something in terms of two alternatives called alternants |
Hypothetical Proposition |
A conditional statement that affirms or denies something in terms of an antecedent (usually expressed as "if") and a consequent (usually expressed as "then") |
Pure Hypothetical Syllogism |
If you do the work, then you will pass the course.
If you pass the course, then you will graduate.
If you do the work, then you will graduate.
(If A, then B
If B, then C
Therefore, if A, then C) |
Mixed Hypothetical Syllogism |
Employs a hypothetical proposition for the first premise but then uses categorical propositions for the second premise and the conclusion.
Modus Pollens ("The way of affirming")
Modus Tollens ("The way of denying") |
Modus Ponens |
"If you do the work, then you will pass the course.
You did the work.
You passed the course."
If A, then B
A
Therefore, B |
Modus Tollens |
"If you do the work, then you pass the course.
You did not pass the course.
You did not do the work."
If A, then B
Not B
Therefore, not A. |
Denying the Antecedent |
"If you do the work, then you will pass the course.
You did not do the work.
You did not pass the course."
If A is true, then B is true.
A is false.
Therefore, B is false. |
Affirming the consequent |
"If you do the work, then you will pass the course.
You passed the course.
You did the work."
If A is true, then B is true.
B is true.
Therefore, A is true. |
Rules of Valid Inference |
(1) The middle term must be distributed at least once in the premises.
(2) If a term is distributed in the conclusion, it must be distributed in the premise.
(3) No conclusion can come from two negative premises.
(4) If one premise is negative, then the conclusion must be negative.
(5) If both premises are affirmative, the conclusion must be affirmative.
(6) If both premises are universal, the conclusion cannot be particular. |
Induction |
Logic made up of arguments which can lead only to a probable cause conclusion, not a necessary one.
No inductive argument can arrive at an absolutely certain conclusion. |
Method of Generalization (Inductive reasoning) |
The most common type of inductive argument, one gathers together identical particular instances & arrives at some form of generalization. |
Method of Analogy (Inductive reasoning) |
An argument from analogy occurs when one observes. |
Probability Calculus (Inductive reasoning) |
A form of inductive argumentation where one reasons on the basis of set rules in determining the likelihood of something occurring given all the possible variables. |
Statistical Reasoning (Inductive reasoning) |
An inductive argument based on the gathering of a sample population and arriving at averages, percentages and general trends. |
Casual Inference (Inductive reasoning) |
An inductive argument that begins with an observed effect and reasons back to its cause. |
Hypothetical Reasoning (Inductive reasoning) |
Inductive reasoning that begins with a problem with an unknown explanation. A hypothesis is formulated and tested with the goal of explaining the problem. |
Hasty Generalization |
Basing a conclusion on an insufficient number of particulars.
"I had a Ford and it was always in the shop and my friend also had frequent problems with his Ford. Ford makes nothing but lemons" |
Sweeping Generalization |
Applying a generalization to a specific case to which the rule does not apply
"Property should be returned to its rightful owner, therefore you should give your drunk friend's car keys to him when he asks for them." |
False Analogy |
Drawing an analogy between two things that are not similar in relevant areas.
"Consumers, who pay for their purchases, get to select what they want when shopping. Therefore students, who pay for their education, should be allowed to pick which courses, assignments and tests they want to take." |
False Cause |
Assuming a causal relation when there is little or no evidence of one.
"I knew it would rain, I just washed my car."
"As violence in the media has arisen so has violence in the streets. We need to stop making violent programs."
"The quality of education in our high schools has been declining for years Clearly teachers aren't doing their job." |
Hypostatization |
Abstract terms are used concretely without clarification, usually through personification.
"Death with dignity"
"If you're open to love, it will find you."
"My stomach is telling me its time to eat!" |
Equivocation |
when the meaning of a significant term changes in the middle of an argument and thus distorts and usually invalidates the conclusion.
"A woman has a right to have an abortion, therefore it is right for her to do so." |
Begging the Question |
The main question or issue is not really addressed, but is ignored or evaded.
"Murder is morally wrong, therefore so is abortion." |
Bifurcation |
Only two options are when other options are possible.
"Either you have faith or you are rational" |
Special Pleading |
An illegitimate double standard is applied that distorts the facts.
"Yes, I do think that all drunk drivers should go to prison, but your honor, he is my son! He is a good boy who just made a mistake!" |
Ad Hominem |
Attacking the person who is making the argument rather than the argument itself.
"He's a liberal, therefore his argument obviously makes no sense." |
Ad Populum |
Appealing to the fact that a belief is popular or commonly believed as evidence for its truthfulness.
"Four out of five Americans choose Zest soda pop over its leading competitor. Eighty percent of American can't be wrong. Buy Zest today" |
Fair Use of Evidence |
Good arguments use evidence fairly and avoid suppressing evidence in favor of a particular position. |
Positive/Negative Approach |
Strongest approach to take in presenting an argument.
Good arguments not only present present positive evidence in favor of the view they are supporting. They also provide negative evidence toward the view they are opposing. |
Explanatory Power |
Considers the quality of the explanation of the facts.
The explanation that can be understood with the least amount of effort , vagueness and ambiguity has the best explanatory power. |
Principle of Parsimony |
Ockman's Razor - "entities should not be multiplied without necessity"; compelling arguments are those which do not contain a lot of unnecessary assumptions or reasoning. |
Counterexample |
an example that refutes the ones that have been suggested in support of the conclusion.
Have the function of weakening an argument by showing that the conclusion does not necessarily follow. |
Steps In Analyzing an Argument ( Step 1): |
Find the conclusion by distinguishing between the premises & the conclusion.
|
Steps In Analyzing an Argument (Step 2): |
Re-write the argument in standard logical order (premises first, conclusion last). |
Steps In Analyzing an Argument (Step 3): |
Do these premises support this conclusion (assuming the premises are true)?
(The most important question) |
Steps In Analyzing an Argument (Step 4): |
Are the premises reliable & true? |
Steps In Analyzing an Argument (Step 5): |
Is the language definite & clear? Does the argument contain "loaded" language? |
Steps In Analyzing an Argument (Step 6): |
If examples are used: are the examples representative? Are there counterexamples (An examples that refutes another example)? |
Steps In Analyzing an Argument (Step 7): |
If an authority is quoted: Is the source reliable & informed? Is the source impartial? Do other sources agree or disagree? Remember: personal attacks don't disqualify arguments. |
Steps In Analyzing an Argument (Step 8): |
If the argument is from cause to effect: Does the argument explain how the cause leads to the effect? Are the correlated events really casually related? |
Steps In Analyzing an Argument (Step 9): |
Does the argument commit a formal or informal fallacy? |