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Lecture

Lecture Two: The Natura of Logic and Reasoning II

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Department
Modes Of Reasoning
Course
MODR 1730
Professor
Philip Mac Ewen
Semester
Fall

Description
Lecture Two: The Nature of Logic and Reasoning II September 14, 2011 Recap of Last Lecture Reasoning or argument is the type of discourse which tries to support a point by appealing to evidence. The point it tries to support is the conclusion and the evidence appealed to is stated in premises. Justice vs. Fairness Are justice and fairness the same thing? Do they overlap at some point or are they two completely different concepts? Types of Arguments Inductive arguments Definition - arguments in which IF the premise or premises is/are true, then the conclusion MAY be true by virtue of this. You may assume anything that is not contradictory, even though they may not be necessarily true. Example: P1 - This piece of iron sinks in water P2 - That piece of iron sinks in water C - All pieces of iron will sink in water There is a large leap between what was observed between the two pieces of iron and what occurs to ALL pieces of iron. This conclusion is believed to be true, although it will never be empirically proven because nobody will ever have observed all pieces of iron placed into water to see what happens. A stronger inductive argument has more proofs. For example, if someone observed 2 pieces of iron vs someone who observed 200 pieces of iron. The second argument would be stronger because more were observed. Example: P1 - My first former husband, who was a hard worker, was no good. P2 - My second former husband, who was a banker, was no good. P3 - My third former husband, who was a world famous actor, was no good. C - No men are good. This is an inductive argument because the premises are assumed to be true because they do not contradict one another, therefore the conclusion makes sense (based on the examples given) even though it may not be true. Deductive Arguments Definition - arguments in which the truth of the conclusions either follows necessarily from the premise/s IF it/they is/are true or necessarily does not follow form the premise/s EVEN IF it/they is/are true. There are valid and invalid deductive arguments. Examples - P1 - All pieces of iron will sink in water. C - This piece of iron sinks in water. In this case, the premise is assumed to be true however it cannot be proven whether or not it truly is. The conclusion follows the premise assuming it is true. P1 - 2=(1+1) P2 - 4=(1+1)+(1+1) P3 - 2+2 = (1+1)+(1+1) C - 2+2=4 This is the best type of deductive argument because none of the premises can be disputed or questioned. P1 - My cat is Felix P2 - My friends cat is Felix P3 - My friends friends cat is Felix C - My cat, my friends cat and my friends friends cat are all Felixes This is true assuming that all the p
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