Be Reasonable! Recognize and Avoid Logical Fallacies

Logical Fallacies - Inaccurate or misleading arguments - Errors in reason

Be Reasonable! Recognize and Avoid Logical Fallacies Arguments can be made by using inductive or deductive reasoning supported by sound evidence

Be Reasonable! Recognize and Avoid Logical Fallacies Inductive Reasoning/Arguments - Begin with evidence (specific facts, observations, expert opinion, and so on), draws inferences from the evidence and reaches a general conclusion

Be Reasonable! Recognize and Avoid Logical Fallacies Deductive Reasoning/Arguments –Begin with premises –statements or assumptions on which an argument is based or from which conclusions are drawn. –Moves from general statements (or premises) to specific conclusions. –Process of deduction traditionally illustrated with a syllogism (major premise, minor premise, and conclusion)

Be Reasonable! Recognize and Avoid Logical Fallacies Deductive Process (Syllogism) (Major premise)All good students should get financial aid (Minor premise) Sarah is a good student (Conclusion) Therefore, Sarah should get financial aid

Be Reasonable! Recognize and Avoid Logical Fallacies Deductive Argument Essays Intro - Presents overview of issue - States the thesis Body -Presents evidence - Presents contra-argument Conclusion – concluding statement reinforces thesis

Be Reasonable! Recognize and Avoid Logical Fallacies Inductive Argument Essays Intro - Presents the issue - States the thesis Body - Presents evidence: facts,observations, expert opinions - Draws inferences from the evidence - Presents contra-argument Conclusion – concluding statement reinforces thesis

Be Reasonable! Recognize and Avoid Logical Fallacies Straw Man Fallacy - Misrepresenting an opponent’s position so as to more easily refute it

Be Reasonable! Recognize and Avoid Logical Fallacies Straw Man Fallacy Example Person A: Sunny days are good Person B: If all days are sunny, we’d never have rain and without rain,we’d have famine and death

Be Reasonable! Recognize and Avoid Logical Fallacies Induction Fallacies Slippery Slope Post Hoc Ergo Propter Hoc Red Herring Begging the Question Hasty Generalization

Be Reasonable! Recognize and Avoid Logical Fallacies Slippery Slope Forecasts a series of events (usually disasterous) that will befall one if the first stated step is taken

Be Reasonable! Recognize and Avoid Logical Fallacies Slippery Slope Example If medical researchers continue to increase human longevity, then the population will soar out of control, mass famine will occur, the global economy will collapse, and the very survival of the species will be threatened

Be Reasonable! Recognize and Avoid Logical Fallacies Post Hoc Ergo Propter Hoc After the fact, therefore because of the fact

Be Reasonable! Recognize and Avoid Logical Fallacies Post Hoc Ergo Propter Hoc 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.

Be Reasonable! Recognize and Avoid Logical Fallacies Red Herring An irrelevant topic is presented in order to divert attention from the original issue

Be Reasonable! Recognize and Avoid Logical Fallacies Red Herring Example After listening to a voter’s concern that the community high school needs to receive major funds to improve facilities, the candidate responds: “I’ve asked the school board to review policies”

Be Reasonable! Recognize and Avoid Logical Fallacies Begging the Question Stating a claim that the speaker assumes is beyond dispute, but in fact is disputable; therefore, begging the question

Be Reasonable! Recognize and Avoid Logical Fallacies Begging the Question (Speaking of TV sitcoms) Speaker states: “I enjoy watching those hackneyed shows” Begging the question of Are all such sitcoms hackneyed?

Be Reasonable! Recognize and Avoid Logical Fallacies Hasty Generalization Leaping to a premature conclusion - not because no evidence is provided but because the evidence is insufficient

Be Reasonable! Recognize and Avoid Logical Fallacies Hasty Generalization Speaker claims that burglary has increased in her neighborhood and gives as only evidence that two houses on the block have been robbed.

Be Reasonable! Recognize and Avoid Logical Fallacies Deduction Fallacies Fails to connect premises to conclusion Ad Hominem Non Sequitur

Be Reasonable! Recognize and Avoid Logical Fallacies Ad Hominem Speaker argues against an individual’s qualifications by attacking his or her personal life or tries to create negative link between life and work

Be Reasonable! Recognize and Avoid Logical Fallacies Ad Hominem Sherwood would not make a good mayor because he spends too much of his time reading murder mysteries.

Be Reasonable! Recognize and Avoid Logical Fallacies Non Sequitur It does not follow An assertion cannot be tied logically to the premise it attempts to demonstrate

Be Reasonable! Recognize and Avoid Logical Fallacies Non Sequitur Premise: “Nellie is obsessed with basketball” Assertion: “because she attends a basketball game every week”