Theory Fallacy Evaluating Arguments
Formal Fallacy (Structure Flaw) Affirming the Consequent: if A then B, B, thus A invalid version of Modus Ponens (affirming the antecedent) Courtney will go to the movie only if she finishes her homework. She finished her homework, so she will go to the movie.
Denying the Antecedent: if A then B, not A, thus B Invalid version of Modus Tollens (denying the consequent) Courtney will go to the movie only if she finishes her homework. She didn't go to the movie, so she didn't finish her homework.
Exclusive Or Fallacy: occurs when an "or" that is inclusive is mistakenly read as being exclusive Courtney will either go to the movie or she will finish her homework. She went to a movie, so she didn't finish her homework.
Illicit Predicate Instantiation I All S's are P's, x is a P, so x is an S All humans are mortal, Socrates is mortal, thus Socrates is a human Illicit Predicate Instantiation II All S's are P's, x is not an S, so x is not a P All humans are mortal, Socrates is not a human, thus Socrates is not mortal
Illicit Universal Syllogism I All A's are B's, all B's are C's, thus all C's are A's All dogs are mammals, all mammals are animals, so all animals are dogs Illicit Universal Syllogism II All A's are B's, all A's are C's, so all C's are B's All executives are well paid, all executives are stockholders, so all stockholders are well paid.
Fallacies of Relevancy Genetic Fallacy: the origins of source or the reasons are criticized instead of the cogency of the reason offered for a claim The Chicago Tribune editorial yesterday advocated raising taxes to support social programs. This is what we'd expect from a liberal newspaper
Appeal to the Person (ad hominem): The person offering the argument is attacked in terms of person characteristics, their circumstances, or because of their actions. Species of genetic fallacy Has 3 subspecies o AH abusive: character attacked; Bill Clinton's endorsement of his wife for the Democratic nomination can hardly be taken seriously given his own "ethics." o AH circumstantial: arguers circumstances attacked; The president of the teachers' union is advocating higher wagges for teachers, but she herself has much to gain o AH tu quoque: claim attacked because inconsistent with behavior; My father says I should give up smoking, but he smokes a pack a day. I can't take his arguments seriously
Equivocation: When a term is used in 2 different senses in the course of an argument
Argument from Ignorance When it is argued either that p is true because it has not been disproven or p is false because it has not been disproven There is no conclusive proof for God's existence, and so God exists God exists because no-one has conclusively disproven God's existence
Red Herring Arguer attempts to focus attention away from the issue at hand to an unrelated issue, thereby winning the argument by default You claim that our company has not done enough to reduce pollution. But what about other companies, they're not doing much either. And they're not doing much because the government has not given them any guidelines...
Straw Man A position the arguer is not arguing for is attributed to them and attacked vs. their actual claim Species of Red Herring The Senator is arguing for universal health care. But that is tantamount to arguing for socialism. Socialism is something we must avoid
Appeal to Emotion A person argues for a claim by playing on the emotions of the listener Two types: o Appeal to force involves trying to persuade someone to accept your claim by an implied threat; You need to vote for hiring X vs. Y. Remember, you are soon coming up for a performance evaluation o Appeal to pity involves trying to persuade someone to accept your claim by appealing to their sympathy; You should hire me for this job since if you don't I won't be able to feed my kids
Appeal to popularity Trying to persuade a person or group to accept a claim based on irrelevant premise that everyone accepts it (popular opinion) or that you will be more liked if you too accept the claim You should buy a Honda, because all your co-workers have one. You don't want to be unpopular "mob mentality" like Hitler's speeches to the masses
Appeal to Tradition Persuade to accept a claim or to do something because this is the way it's always been done Son, you should vote for the Republican candidate because the that's way our family has always voted
Fallacy of Composition Involves the mistaken assumption that what is true of the parts is always true of the whole Each part of the engine was built to. specifications and works perfectly. Thus, the engine as a whole will work perfectly Fallacy of Division Involves the mistaken assumption that what is true of the whole is true of the parts
The class average was a B. Jan was in that class, so she must have gotten a B.
Fallacies of Problematic Premise Begging the Question Merely a restatement of the conclusion, has no support; P therefore P Argument is formally valid There is a Providential order to the universe, and hence God exists
False Dilemma Are DS's with a problematic disjunctive premise P: A or B (ignores third option) P: not-A C:B George Bush has said that either you're with us or you're against us. The third ignored option by Bush is that a country is neutral
Slippery Slope P: A leads to B; P:B leads to C; P: C leads to D; P: We don't want D; C: not-A We can't allow tapping phones of suspected terrorists. If we do, then soon the government will begin tapping phones of relatives of terrorists. And if they do that, they will start tapping phones of innocent citizens. If that happens, freedom will be restricted. But that's unacceptable
Hasty Generalization: When there is insufficient evidence offered in support of a claim; either the sample is too small or its is not representative Weak inductive arguments 245 or 300 chemistry students interviewed at the university said they will vote Democrat in the next election. Thus, most students at the university will vote Democrat in the next election
Faulty analogy Two things that are like in one respect are said to be alike in another respect Weak inductive argument Like a programmed computer, the human mind stores memories. Since a computer has total recall, it follows that humans have total recall
Additional Fallacies Accident Confusion between something that's generally true with its being universally ture Everyone has the right to free speech. Thus, hate groups have a right to spread their literature
False Cause Faulty casual inferences A caused B on the basis that A preceded B in time o All 4 of us ate at the restaurant last night, and the next day we all became ill. Thus, it's something we ate at the restaurant Oversimplification ignoring additional causal factors o My son would study harder if only he understood the need for an education Confusing cause with effect o The most productive employees at our firm are paid the highest wages. Thus, high wages cause productivity
Complex question A question is asked such that no matter how it is answered, the arguer's claim is verified Police to suspect: Were you running when you stole the purse? Suspect: I can't run I have bad legs. Police: Then you were walking when you stole the purse.
Suppressed Evidence Arguer reaches conclusion by only considering some of the available evidence "Teachers make more money than they did 10 years ago. Thus, they have no right to complain about their wages
Subjectivism Something is true simply on the grounds that one believes it to be true What is morally wrong is what a person believes in their heart is wrong. I believe in my heart that euthanasia is morally wrong, so Jack Kevorkian should have been jailed. "Wishful thinking" The company just can't fold because I have so many bills. I know it will be OK, I'm not worried
Two Wrongs A morally or prudentially wrong act is justified on the grounds that it will right a previous wrong The death penalty is morally justified for murder because the convicted murderer showed no regard for the life of their victim.
Inconsistency Arguer contradicts themselves in the course of an argument P and not-P While it is important to adhere to the letter of the law, an exception should be made in this case because the defendant has already paid a heavy price in terms of lawyer's fees and endless trials. They should be exempt from mandatory sentencing.
Irrelevant Conclusion A premise that is relevant to one particular conclusion is instead used to support a conclusion to which it is not strictly relevant The schools in our district are seriously underfunded. They don't have the money to buy computers and books, which means the quality of education is suffering. It follows that we need to increase taxes as soon as possible.