Transcript Analogical Argument

ANALOGICAL ARGUMENT
Prof. Dr. John JA Burke
MLA
DEFINITION
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Analogical argument
• Proceeds from the similarity of two or more things in one or more respects to the
similarity of those things in some further respect
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Schematically
• “A”,”B”,”C”, and “D” are any entities; P, Q, R, are any attributes or “respects”
• “a, b, c, d” all have the attributes P and Q
• “a, b, c” all have the attribute R
• Therefore d probably has the attribute R
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Analogy is an inductive argument
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Inferences from past experience to what future will hold
NOT ALL ANALOGIES ARE ARGUMENTS
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Analogies are often used in literature or as a means of explanation
• These are non-argumentative analogies
• Example, the genome project is wholly analogous to the creation of the periodic table
in chemistry
• Steve Jobs is the Warren Buffet of computer technology
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Arguments have premises and assert conclusions
EXERCISES: ANALOGICAL ARGUMENTS V. NONARGUMENTATIVE ANALOGIES
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I am not anti-Semitic, I am just anti-Zionist is the equivalent of I am not anti-American, I
just think the United States should not exist.
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Question
• Distinguish
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Instead of investing in the future, we throw money away on absurd luxuries, finance
corrupt and hostile oil-rich countries, pollute our atmosphere and increase our trade
deficit. Sort of like driving a `hummer to the shopping mall.
• Distinguish
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One sure thing is that melting sea ice cannot be implicated in the coastal flooding that
many global warming models have projected. Just as melting ice cubes do not cause a
glass of water to overflow, melting sea ice does not increase oceanic volume. Any future
rise in sea level would result from glaciers melting on land
• Distinguish
APPRAISING ANALOGICAL ARGUMENTS
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Number of entities
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Larger the number of entities the stronger the argument
• No ration between number and probability
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Variety of the instances in the premises
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More dissimilar instances mentioned, the stronger the argument
Number of similar respects
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Greater of number of respects of similarity of entity in conclusion to entities in premises,
stronger the argument
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Relevance
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Dis-analogies
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Claim that the conclusion makes
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More modest the claim, stronger the argument
PRACTICE EXERCISES
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Selected from Text
PROBABILITY
Prof. Dr. John JA Burke
ALTERNATIVE CONCEPTIONS
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Probability is the central evaluative concept in inductive logic
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Number assigned to probability of an event
• Numerical coefficient of probability
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Two uses
• A priori conception of probability [no empirical data/no trials]
• Relative frequency conception of probability [empirical data]
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Probability is relative to evidence
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Numerical assignment can be given to event
CALCULUS OF PROBABILITY
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Two forms
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Joint occurrences: probability of two events both happening
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Alternative occurrences: probability that at least one of given set of alternative events will
occur
Joint occurrences
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Product theorem
• Probability of joint occurrence of two independent events equals the product fo their
separate probabilities
• P(a and b) = P(a) x P(b)
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Roll of dice
• Each die has 6 sides; showing 6 = 1/6 P(a) = 1/6
• P(b) equally has chance of 1/6
• Hence two dice showing 12 = P(a) x P(b) = 1/36
EXERCISES
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