PSYC105 Lecture Notes - Lecture 5: Dermatology, Modus Tollens, Deductive Reasoning
PSYCH105 - CRITICAL THINKING IN PSYCHOLOGY
Wk. 5 - Purpose of Arguments
Arguments:
A form of thinking in which in which certain reasons (i.e., premises) are offered to
support a conclusion.
Reason: marijuana is less likely to excite violence than alcohol
Reason: moderate marijuana use is less damaging to the lungs than tobacco
Reason: Legislation of marijuana would allow for taxation
Conclusion: therefore, marijuana should be legalized
Decide
Reason: I’ve always been interested in human behaviour
Reason: psychology is a diverse field with many job opportunities
Conclusion: I will apply to study psychology at university
Explain
Reason: I did not commence working on my assignment until Monday night
Reason: I had a headache all day Tuesday
Conclusion: Therefore, I did not submit my assignment by the due date of
Wednesday
Predict
Reason: If I wake up at 7am I can catch the 8am bus to uni
Reason: If I catch the 8am bus I arrive at uni on time
Conclusion: It follows that if I set my alarm for 7am I will arrive at uni on
time tomorrow morning
Persuade
Reason: Research has linked smoking cigarettes to lung cancer
Reason: Products known to be bad for our health should not be legalised
Conclusion: Therefore, cigarettes should not be legalised
Evaluating Arguments
Truth
How true are the supporting reasons?
E.g., is there any evidence offered?, can the source be trusted?
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Validity
Do the reasons support the conclusion?
Valid argument
When reasons support the conclusion so that the conclusion follows from the
reasons offered
Invalid argument
When reasons do not support the conclusion so that the conclusion does not
follow from the reasons offered
Validity is a property of the arguments structure
Q1.
Reason: All pigs are purple in colour
Reason: Anything that is purple is an animal
Conclusion: Therefore, all pigs are animals
Valid or invalid?
VALID – from the information required. It is valid argument in structure but not a
sound argument as the reasons given are not true
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find more resources at oneclass.com
Q2.
Reason: Jessica Simpson uses pro-active
Reason: Jessica Simpson is a celebrity
Conclusion: Therefore, I should use proactive
Valid or invalid?
INVALID – invalid in structure and the argument is illogical in clarity as she has no
expertise in this field of dermatology
Evaluating the Soundness of Arguments
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find more resources at oneclass.com
Document Summary
A form of thinking in which in which certain reasons (i. e. , premises) are offered to support a conclusion. Reason: marijuana is less likely to excite violence than alcohol. Reason: moderate marijuana use is less damaging to the lungs than tobacco. Reason: legislation of marijuana would allow for taxation. Reason: i"ve always been interested in human behaviour. Reason: psychology is a diverse field with many job opportunities. Conclusion: i will apply to study psychology at university. Reason: i did not commence working on my assignment until monday night. Reason: i had a headache all day tuesday. Conclusion: therefore, i did not submit my assignment by the due date of. Reason: if i wake up at 7am i can catch the 8am bus to uni. Reason: if i catch the 8am bus i arrive at uni on time. Conclusion: it follows that if i set my alarm for 7am i will arrive at uni on time tomorrow morning.
