Topic 3: Argumentation
• Argument is a claim put forward and defended with reasons. • Arguments are composed of:
• Statement: A sentence that can sensibly be regarded as either true or false. • 2 things about statements:
1. A sentence may be used to express more than one statement. 2. Not all sentences are statements.
3. Consider the CONTEXT in which particular expression is used.
Identifying Premises and Conclusions
1. Premise indicators
• Since, for, seeing that, in view of the fact that, because, given that, being that, as, as indicated by.
2. Conclusion indicators
• Therefore, hence, so, it follows that, that is why, wherefore, as a result, suggests that, thus, consequently, accordingly, for this reason, which shows that, implies that, we may infer that, proves that.
• 2 types of arguments:
• 5 types of nonarguments:
2. Unsupported statements of belief and opinion
3. Conditional statements
• To convey information about a subject, not to offer reasons why one statement should be accepted on the basis of others.
Unsupported statements of belief/opinion
• No claim that these statements follow from or imply any other statements.
• “if-then” statements.
• Intended to provide examples of a claim rather than to prove or support the claim.
• Try to show why something is the case, not to prove that it is the case.
• 2 questions:
1. Are the premises true?
2. Can the premises provide “good reasons” for its conclusion?
Are the premises true?
• When is it reasonable to accept a premise?
• It is true if:
1. it is supported by evidence
2. it uses Principle of Rational Acceptance.
• Principle of Rational Acceptance:
1. The claim does not conflict with personal experience
2. Does the claim conflict with our background beliefs?
3. Does the claim come from a credible source?
• Good reasons to doubt the credibility of a source may incude: 1. The source is not a genuine expert or authority.
2. The source is speaking outside the area of his experience. 3. The source is biased/has motive to lie or mislead. 4. The accuracy of the source’s personal observations @ experiences is doubtful. 5. The source is a media source/internet source that is generally unreliable. 6. The claim made by the source is, in itself, highly implausible @ unlikely.
Can the premise provide `good reasons’ for its conclusion? • 2 kinds of arguments:
1. Deductive (Topic 4)
2. Inductive (Topic 5)
• Good Argument is when:
1. All the premises are true
2. The premises provide good reasons to accept the conclusion 3. Meet the standards of critical thinking discussed in Topic 1.
Topic 4: Deductive Arguments
• Try to prove that their conclusions with rigorous, inescapable logic. • Attempt to show that conclusions must be true given the premises asserted.
Common Patterns of Deductive Reasoning
1. Hypothetical Syllogism
Syllogism: A three-line argument, consists of exactly 2 premises and a conclusion. Several types:
a) Modus ponens
b) Chain argument
c) Modus tollens
d) Denying the antecedent
e) Affirming the consequent
2. Categorical syllogism
3-line argument in which each statement begins with the word all, some, @ no.
3. Argument by elimination
Seeks to logically rule out various possibilities until only a single possibility remains.
4. Argument based on Mathematics
The conclusion is certain, not mere likely @ probable.
5. Argument from definition
The conclusion is presented as being true by definition.
Valid deductive argument: Logically reliable deductive argument (the conclusion really does follow necessarily from the premises)
Invalid deductive argument: The conclusion does not follow necessarily from the premises.
Topic 5: Inductive Arguments
• Simply claim that conclusions are likely @ probable given the premises offered.
Common Patterns of Inductive Reasoning
1. Inductive Generalization
An argument in which a generalization is claimed to be probably true based on information about some members of a particular class.
2. Predictive argument
A prediction that is defended with reasons.
3. Argument from authority
Asserts a claim and then supports that claim by citing some presumed authority @ witness who has said that the claim is true.
4. Causal argument
Asserts or denies that something is the cause of something else.
5. Statistical argument
Rests on statistical evidence.
6. Argument from Analogy
The conclusion is claimed to depend on comparison between 2 @ more things.
Strong inductive argument: Logically reliable inductive argument. The conclusion is probably true if the premises are true.
Weak inductive argument: The conclusion is not probably true even if the premises are true.
|Key differences | |Deductive |Inductive | |1. If the premises are true, then the conclusion must be true. |1. If the premises are true, then the conclusion is probably | | |true. | |2. The conclusion follows necessarily from the premises. |2. The premises follows probably from the premises. | |3. The premises provide conclusive evidence for the truth of the |3. The premises provide good (but not conclusive) evidence for | |conclusion. |the truth of the conclusions. | |4. It is impossible for all the premises to be true and |4. It is unlikely that the premises are true and the conclusion | |conclusion false. |false. | |5. It is logically inconsistent to assert the premises and deny |5. Although it is logically consistent to assert the premises and| |the conclusion (if you accept the premises, then you must accept |deny the conclusion, the conclusion is probably true if the | |the conclusion.) |premises are true. |
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