Common Reasoning Fallacies

1. Common Reasoning Fallacies • Errors arising from ambiguity • Circular arguments that beg the question • Use of unwarranted assumptions • Fallacies involving missing evidence • Incorrectly identified causation • Premises irrelevant to the stated conclusion • Appeal to emotion/loyalty/authority/… • Diversion from the main point • Incorrect deductive inference

2. Common Reasoning Fallacies • Since computer A has a 1.1 GHz Celeron processor and computer B has a 800 MHz G4 processor, computer A will run programs faster than computer B. • What type of fallacy is illustrated in this argument?

3. Common Reasoning Fallacies • The criteria for patentability are originality, novelty, utility, and nonobviousness, and my invention is original, novel, useful, and nonobvious, therefore my invention deserves to be patented. • What type of fallacy is illustrated in this argument?

4. Common Reasoning Fallacies • Professor XYZ proposed a change in the curriculum and professor XYZ has low student evaluations, so the proposed change in the curriculum should not be considered. • What type of fallacy is illustrated in this argument?

5. Common Reasoning Fallacies • We certainly would not grant constitutional protections to Osama Bin Laden when he is captured and John Walker was a follower of Osama, so John Walker does not deserve constitutional protections and should be tried by a military tribunal. • What type of fallacy is illustrated in this argument?

6. Common Reasoning Fallacies • Since our testing did not reveal any new bugs, there are no remaining bugs in the software. • What type of fallacy is illustrated in this argument?

7. Common Reasoning Fallacies • Paper supplier XYZ is the smallest supplier in town therefore we should purchase all of our paper supplies from XYZ in order to help the underdog. • What type of fallacy is illustrated in this argument?

8. Common Reasoning Fallacies • Since John is in charge of selecting a new team leader and since John and Bill played golf last week, when Bill was named the new team leader it is obvious John was prejudiced in favor of his golfing pals. • What type of fallacy is illustrated in this argument?

9. Common Reasoning Fallacies • If the country is in a recession then our business will be slow, but the country is not in recession therefore our business will be brisk. • What type of fallacy is illustrated in this argument?

10. Common Reasoning Fallacies • The six month project being developed by three programmers appears to be two months late, so add one more programmer and the project can be completed on schedule. • What type of fallacy is illustrated in this argument?