ITEM 1
A professor tells the students at the beginning of the term that, in order to pass the course, they will have to come to class regularly, read the daily assignments, participate in class discussions, take all tests and examinations, and submit a research paper. Some students have faithfully met such conditions and then have experienced genuine surprise when they failed the course.
Source: http://bellsouthpwp.net/s/e/sean_c_rhoades/LogicalDebate/FallacyOfTheDay/Fallacy12.htm
Analysis:
=> Necessary and Sufficient Conditions
In the case in question, the professor mentioned the necessary but not the sufficient condition for passing the course. However, students misunderstood that they were sufficient conditions. Sufficient condition for passing the exam would presumably include getting passing grades on the tests and the research paper. Such puzzlement could possibly be eliminated if the students understood the difference between the necessary and sufficient condition for passing the course.
ITEM 2:
Bill: “You know, those feminists all hate men.”
Joe: “Really?”
Bill: “Yeah. I was in my philosophy class the other day and that Rachel chick gave a presentation.”
Joe: “Which Rachel?”
Bill: “You know her. She’s the one that runs that feminist group over at the Women’s Center. She said that men are all sexist pigs. I asked her why she believed this and she said that her last few boyfriends were real sexist pigs. ”
Joe: “That doesn’t sound like a good reason to believe that all of us are pigs.”
Bill: “That was what I said.”
Joe: “What did she say?”
Bill: “She said that she had seen enough of men to know we are all pigs. She obviously hates all men.”
Joe: “So you think all feminists are like her?”
Bill: “Sure. They all hate men.”
Source:
http://www.nizkor.org/features/fallacies/hasty-generalization.html
Analysis:
– Rachel’s argument
Premise 1: Her last few boyfriends were real sexist pigs
Premise 2: (hidden premise) her boyfriends are men
Conclusion: All men are all sexist pigs
This is hasty generalization because she just met some men who were real sexist pigs; however, she concludes that all men are sexist pigs.
– Bill’s argument:
Premise 1: Rachel said that she hate men
Premise 2: Rachel runs that feminist group over at the Women’s Center
Premise 3: All members of a group agree with their leader
Conclusion: All feminists hate men.
Bill only know one women ( a leader of feminist group) who said that she hate men, he concludes all feminists hate men, so this is a hasty generalization argument.
*Both of these arguments are the speakers draw a conclusion about a whole group based on a sample that is not large enough. In fact, they only know one or few people but they think what’s true for a member is true for the whole group (false premise).
ITEM 3:
The Republicans pass a new tax reform law that benefits wealthy Americans. Shortly thereafter the economy takes a nose dive. The Democrats claim that the tax reform caused the economic woes and they push to get rid of it.
Source:
http://www.zionism-israel.com/Fallacies/post-hoc.html
Analysis:
=> Post Hoc
The fallacy involves concluding that a new tax reform law causes economy’s nosedive because the tax reform occurs before the economy’s nosedive, and there is not sufficient evidence to actually warrant such a claim. In the example, the nosedive of economy is blamed for passing a new tax reform law just simply because this law happens before the decline of the economy despite the fact that this decrease would result from many other reasons such as instable politics, natural disasters, etc.