Lecture 6 Deductive Reasoning (II)

Lecture 6 Deductive Reasoning (II) - 1 CC2002 Semester One...

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Unformatted text preview: 1 CC2002 Semester One 2011/12 Creative and Critical Thinking 創創創創創創創創創 Lecture 6 Deductive Reasoning (II) 2 The ambiguity of 創創創創 創創創創創創創創創創創創創創創創創 1. Possible 創創 ( 創創創 ) (logical possibility) 2. Probable 創創 ( 創創創 ) (empirical probability) 創創創創創創創創創創創創創創創創 沒沒沒沒 創創 創創創創創創創創創創創創創 ( 創創創 ) 創 創 ( 創創創 ) 創創創創創創 (= 創創創 創 ) 創 3 What strong arguments are A strong ( 沒 ) argument: 1. Invalid ( 創創創 ) 2. Given that the premise(s) is(are) true, it is very likely ( 創創創 ) that the conclusion is true . E.g. 1. 99.9% 創 CCT 創創創創創創創創 2. 創創創 CCT 創創創 3. 創創創創創創創創創創 1. Peter bought one ticket in a fair lottery with ten million tickets. 2. So Peter is not going to win the lottery. 4 What strong arguments are 沒 創創創創 創創創創創 沒 創創創創創創創創創創創創創創創 創創創創創創創創 (>50% 創 <100%) 創創創創創創 5 Deductive Argument ( 創創創創 ) A deductive argument is an argument in which the conclusion is claimed to be justified by (or to follow from) the premise(s) with (logical) necessity ( 創創創 ), or it is claimed to be (logical) necessary that the conclusion is true if all the premises are true. 創創創創創創創創創創創創創創創創 創 創 180 創創 All whales are mammals. All mammals are animals. Hence, all whales must be animals. Alan is a father. Therefore, it is necessary that Alan is a male. Please note that: Deductive arguments ≠ valid arguments 6 Inductive Argument ( 創創創創 ) An inductive argument is an argument in which the conclusion is claimed to be justified by (or to follow from) the premise(s) with a certain degree of probability ( 創創創 ), namely > 0.5 , or The conclusion is claimed to be probably true ( 創創創 ), (i.e., more likely to be true than false) if all the premises are true. 95% of our students wear glasses. Joe is our student. Therefore, Joe probably( 創 創創 ) wears glasses. 創創創創創創創創創創創創創創創創創創創創創創創創創創創 創創創創創創創創創創 Mary is a six-year-old girl. Therefore, it is very likely that Mary cannot finish 100m in 15 seconds....
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Lecture 6 Deductive Reasoning (II) - 1 CC2002 Semester One...

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