Richard L Epstein

by Critical Thinking (3rd Edition) (pdf)

  3. Dick: Nixon was a crook.

  Zoe: No he wasn't. Remember that famous "Checkers" speech where he said so?

  Dick: That was just political evasion. Anyway, you can't just take someone's word that

  he's not a criminal, especially if he's a politician. He directed the break-in at the

  Democratic Party Headquarters.

  Zoe: They never showed that he did that.

  Dick: That's because his accomplices like Haldemann were covering up. That's why

  they got pardoned. And he used the FBI against his enemies. He was a criminal.

  It was stupid for Clinton to make a speech honoring him when he died.

  Zoe: Maybe Clinton was doing it so that when he dies someone will make a speech

  for him, too.

  Glossary

  Terms used only in an appendix are not listed here, but may be found in the Index.

  Affirming the consequent Reasoning in the form: If A, then B; B; so A. Usually weak.

  All Usually means "every single one, no exceptions." Sometimes "all" is best understood as "every single one, and there is at least one."

  Alternatives The claims that are the parts of an "or" claim.

  Ambiguous sentence A sentence that can be understood in two or a very few obvious ways.

  Analogy, reasoning by A comparison becomes reasoning by analogy when it is part of an

  argument: On one side of the comparison we draw a conclusion, so on the other side we

  should conclude the same.

  Anecdotal evidence Claims about a sample of one or very few used as evidence for a

  generalization. The claims about the sample in a hasty generalization.

  Antecedent The claim A in a conditional claim "If A, then B . "

  Appeal to authority An argument that uses or requires as premise: (Almost) anything that says about _ _ _ _ _ is true.

  Appeal to common belief An argument that uses or requires as premise: If (almost)

  everyone else (in this group) believes it, then it's true.

  Appeal to emotion An argument that uses or requires as premise: You should believe or

  do if you feel . (e.g., fear, pity, s p i t e , . . . )

  Apple polishing A feel-good argument that appeals to vanity.

  Apples and oranges A meaningless comparison.

  Arguing backwards Reasoning that the premises of an argument are true because the

  conclusion is true and the argument is valid or strong. See also Affirming the consequent.

  Arguing backwards with all Reasoning in the form: All S are P; a is P; so a is S.

  Usually weak.

  Arguing backwards with almost all Reasoning in the form: Almost all S are P; a is P; so a is S. Usually weak.

  Arguing backwards with no Reasoning in the form: All S are P; no Q is S; so no Q is P.

  Usually weak.

  Argument An attempt to convince someone (possibly yourself) that a particular claim,

  called the conclusion, is true. The rest of the argument is a collection of claims called

  premises, which are given as the reasons for believing the conclusion is true.

  391

  392 GLOSSARY

  Assertion A claim that is put forward as true.

  Average (or mean) of a collection of numbers The number obtained by adding all the

  values and then dividing by the number of items.

  Begging the question An argument that uses a premise that is no more plausible than the

  conclusion.

  Biased sample A sample that is not representative.

  Calling in your debts An argument that uses or requires as premise: You should believe

  or do if you owe a favor.

  Causal claim A claim that is or can be rewritten as "— causes (or caused) —."

  Causal factor One of several claims that jointly qualify as describing the cause.

  Cause See Necessary criteria for cause and effect.

  Cause in a population A claim that if the cause is present, there is a higher probability the effect will follow than if the cause were not present.

  Claim A declarative sentence used in such a way that it is either true or false (but not both).

  Composition, fallacy of Reasoning that what is true of (or good for) the individual must

  also be true of (or good for) the group, or vice-versa.

  Compound claim A claim composed of other claims, but which has to be viewed as just

  one claim.

  Conclusion The claim whose truth an argument is intended to establish.

  Conditional claim A compound claim that can be rewritten as an " i f . . . then . . . " claim that must have the same truth-value.

  Confidence level The percentage of the time that the same sampling method would give a

  result that is a true generalization. The strength of the generalization.

  Confusing objective and subjective Calling a claim objective when it is really subjective,

  or vice-versa.

  Consequent The claim B in a conditional claim "If A, then B . "

  Content fallacy An argument that uses or requires for repair a particular kind of (generic)

  premise that, if false or dubious, classifies the argument as a fallacy.

  Contradictory of a claim A contradictory of a claim is one that has the opposite truth-

  value in all possible circumstances. Sometimes called a negation of a claim.

  • Contradictory of "A or B" is "Not A and not B . "

  • Contradictory of "A and B" is "Not A or not B . "

  • Contradictory of "If A, then B" is "A but not B . "

  Contrapositive The contrapositive of "If A, then B" is "If not B, then not A." The contrapositive is true exactly when the original conditional is true.

  Control group See Controlled experiment: cause-to-effect.

  GLOSSARY 393

  Controlled experiment: cause-to-effect An experiment to establish cause in a population.

  Two randomly chosen samples are used. One is administered the cause, and the other, called

  the control group, is not administered the cause. See also Uncontrolled experiment.

  Criteria for Accepting or Rejecting a Claim In the order in which they should be applied:

  Accept: We know the claim is true from our own experience.

  Reject: We know the claim is false from our own experience.

  (Exceptions: We have good reason to doubt our memory or our perception;

  the claim contradicts other experiences of ours; and there is a good argument

  against the claim.)

  Reject: The claim contradicts other claims we know to be true.

  Accept: The claim is made by someone we know and trust, and the person is an

  authority on this kind of claim.

  Accept: The claim is made by a reputable authority we can trust as an expert

  about this kind of claim who has no motive to mislead.

  Accept: The claim is put forward by a reputable journal or reference source.

  Accept: The claim is in a media source that's usually reliable and has no obvious

  motive to mislead, if the source is named.

  Critical thinking Evaluating whether we should be convinced that some claim is true or

  some argument is good, as well as formulating good arguments.

  Definition An explanation or stipulation of how to use a word or phrase. A definition is

  not a claim. See also Good definition; Persuasive definition.

  Denying the antecedent Reasoning in the form: If A, then B; not A; so not B. Usually

  weak.

  Descriptive claim A claim that says what is. Compare Prescriptive claim.

  Direct way of reasoning with all Reasoning in the form: All S are P; a is S;

  so a is P. Valid.

  Direct way of reasoning with almost all Reasoning in the form: Almost all S are P;

  a is S; so a is P. Usuall
y strong.

  Direct way of reasoning with conditionals Reasoning in the form: If A, then B; A; so B.

  Valid. Also called modus ponens.

  Direct way of reasoning with no Reasoning in the form: All S are P; no Q is P; so no Q

  is S. Valid.

  Direct ways of refuting an argument See Refuting an argument directly.

  Disjunctive syllogism See Excluding possibilities.

  Downplayer A word or phrase that minimizes the significance of a claim.

  Drawing the line fallacy A type of bad argument which assumes that if you can't make

  the difference precise, then there is no difference.

  Dubious claim See Implausible claim.

  394 GLOSSARY

  Dysphemism A word or phrase that makes something sound worse than a neutral

  description. See also Euphemism.

  Effect See Necessary criteria for cause and effect.

  Euphemism A word or phrase that makes something sound better than a neutral

  description. See also Dysphemism.

  Evidence A claim or claims that give some reason to believe another claim.

  Excluding possibilities Reasoning in the form: A or B; not A; so B (can use more

  alternatives). Valid. Also called disjunctive syllogism.

  Fallacy An argument of one of the types that have been agreed to be so bad as to be

  unrepairable. See also Content fallacy; Structural fallacy.

  False dilemma A use of excluding possibilities, but the "or" claim isn't plausible.

  Sometimes the false or dubious "or" claim itself is called the "false dilemma."

  Feel-good argument An argument that uses or requires as premise: You should believe or

  do if it makes you feel good.

  Foreseeable consequence of a cause A claim that becomes true after the actual cause, yet

  because it is a consequence of that cause is not counted as part of the cause.

  Gambler's fallacy An argument that uses or requires as premise: A run of events of a

  certain kind makes a run of contrary events more likely in order to even up the probabilities.

  General cause and effect A causal claim that is true if and only if many particular cause

  and effect claims are true. See also Particular cause and effect.

  General claim A claim that asserts something in a general way about all or a part of a

  collection.

  Generalizing Concluding a claim about a group, the population, from a claim about some part of it, the sample. To generalize is to make an argument. Sometimes the general claim

  is called the generalization; sometimes that word is used for the whole argument. The

  knowledge of the sample is called the inductive evidence for the generalization. See also Premises needed for a good generalization.

  Good argument See Tests for an argument to be good.

  Good definition A definition in which (1) The words doing the defining are clear and

  better understood than the word or phrase being defined, and (2) The word or phrase being

  defined and the words doing the defining can be used interchangeably.

  Guide to Repairing Arguments Given an (implicit) argument that is apparently defective,

  we are justified in adding a premise or conclusion if it satisfies all three of the following:

  • The argument becomes stronger or valid.

  • The premise is plausible and would seem plausible to the other person.

  • The premise is more plausible than the conclusion.

  If the argument is then valid or strong, we may delete a premise if doing so does not make

  the argument worse. See also Unrepairable arguments.

  GLOSSARY 395

  Haphazard sampling Choosing a sample with no intentional bias. Not usually reliable for

  generalizing. Compare Random sampling.

  Hasty generalization Generalizing from a sample that is much too small.

  Hyperbole An extreme version of an up-player; a gross exaggeration.

  If and only if "A if and only if B" means "If A, then B; and if B then A."

  Impersonal standards See Objective claim.

  Implausible claim A claim that we do not have good reason to believe is true.

  Implying See Inferring and implying.

  Inductive evidence See Generalizing.

  Indicator word A word or phrase added to a claim telling us the role of the claim in an

  argument or what the speaker thinks of the claim or argument. Not part of a claim.

  Indirect way of reasoning with conditionals Reasoning in the form: If A, then B; not B;

  so not A. Valid. Also called modus tollens.

  Inferring and implying When someone leaves a conclusion unstated, he or she is implying

  the conclusion. When you decide that an unstated claim is the conclusion, you are inferring

  that claim. We also say someone is implying a claim if in context it's clear he or she

  believes the claim. In that case we infer that the person believes the claim.

  Innuendo A concealed claim that is particularly unpleasant.

  Intersubjective claim A subjective claim about which (nearly) everyone agrees on.

  Intervening cause A claim that becomes true after the cause and before the effect that is

  not a foreseeable consequence of the original cause and which qualifies as a cause, too.

  Invalid argument An argument that is not valid. Usually classified from strong to weak.

  Irrelevant premise A premise that can be deleted from an argument without making the

  argument any weaker. See also Relevance.

  Issue A claim that is being debated.

  Judging claims {three choices we can make about whether to believe a claim is true)

  • Accept the claim as true.

  • Reject the claim as false.

  • Suspend judgment.

  Law of large numbers If the probability of something occurring is X percent, then over

  the long run the number of times that happens will be about X percent.

  Loaded question A question that conceals a dubious claim that should be argued for rather

  than assumed.

  Margin of error In a generalization, the range within which the actual number for the

  population is claimed to fall.

  396 GLOSSARY

  Mark of irrationality If you recognize that an argument is good, then it is irrational not to accept the conclusion.

  Mean See Average.

  Median of a collection of numbers The midway mark: the number in the collection such

  that there are as many items above it as below it in the collection.

  Mistaking the person for the argument An argument that uses or requires as premise:

  (Almost) any argument that gives about is bad.

  Mistaking the person for the claim An argument that uses or requires as premise:

  (Almost) anything that says about is false.

  Mode of a collection of numbers The number that appears most often in the collection.

  Modus ponens ("way of putting") See Direct way of reasoning with conditionals.

  Modus tollens ("way of taking") See Indirect way of reasoning with conditionals.

  Necessary criteria for cause and effect

  • The cause happened (the claim describing it is true).

  • The effect happened (the claim describing it is true).

  • The cause precedes the effect.

  • It is (nearly) impossible for the cause to happen (be true) and

  the effect not to happen (be false), given the normal conditions.

  • The cause makes a difference—if the cause had not happened (been true),

  the effect would not have happened (been true).

  • There is no common cause.

  Necessary and sufficient conditions A is necessary for B means that "If not A,
<
br />   then not B" is true. A is sufficient for B means that "If A, then B" is true.

  Negation of a claim See Contradictory of a claim.

  No-matter-what argument Reasoning in the form: If A, then B; if not A, then B; so B.

  Valid.

  Normal conditions For a causal claim, the obvious and plausible unstated claims that are

  needed to establish that the relationship between purported cause and purported effect is

  valid or strong.

  Objective claim A claim whose truth-value does not depend on what someone (or

  something) thinks, believes, or feels. An objective claim invokes impersonal standards.

  Only "Only S are P" is equivalent to "All P are S."

  Only if "A only if B" is equivalent to "If not B, then not A." It is also equivalent to

  "If A, then B . "

  Particular cause and effect A claim that this particular cause caused this particular effect, See also General cause and effect.

  GLOSSARY 397

  Perfectionist dilemma An argument with (possibly unstated) premise: Either the situation

  will be completely perfect if we do this, or we shouldn't do it.

  Personal standards See Subjective claim.

  Persuasive definition A claim masquerading as a definition. An attempt to close off

  debate by stating the issue as a definition.

  Phony refutation Concluding that an argument is bad because the person who made the

  argument has done or said something that shows he or she (apparently) does not believe one

  of the premises or the conclusion of the argument. A fallacy.

  Plausible claim A claim that we have good reason to believe is true.

  Population See Generalizing.

  Post hoc ergo propter hoc ("After this, therefore because of this.") Claiming that there is cause and effect solely because this happened after that.

  Premises The claims in an argument that are meant to establish that the conclusion is true.

  Premises needed for a good generalization

  • The sample is representative.

  • The sample is big enough.

  • The sample is studied well.

  Prescriptive claim A claim that says what should be. Compare Descriptive claim.

  Principle of Rational Discussion We assume that the other person who is discussing an

  issue with us or whose arguments we are reading:

  • Knows about the subject under discussion.

  • Is able and willing to reason well.

  • Is not lying.