A comparison of things that are claimed to be similar in some respect, 70, 175, 323, 423
A priori probability
A kind of probability that can be calculated prior to, and independently of, sensory observation, 343--348
Argument
A claim defended with reasons. More precisely, an argument is a set of statements, one of which (called the conclusion) is claimed or intended to be supported by the others (called the premises), 25, 50; cogent, 82--83, 222--223, 310, 312; complex, 32--33; deductive, 52--67, 83; explanation and, 42--43; inductive, 52--62, 67, 71, 83, 305--350; invalid, 74--78, 83; not a fight, 407--409; simple, 32--33; sound, 78, 83, 222--223, 310; strong, 78, 83, 222, 305, 312; uncogent, 82--83, 312; unsound, 78, 83; valid, 74--78, 83, 222, 276, 286; weak, 79-83, 305, 312
Argument from analogy
An argument in which the conclusion is claimed to depend on an analogy (i.e., a comparison or similarity) between two or more things, 70-71, 323-333; constructing, 332-333; evaluating, 325-329; in law, 330; in ethics, 330
Causal argument
An argument that asserts or denies that something causes, has caused, or will cause something else, 69, 334--340
Cogent argument
An inductive argument that is strong and has all true premises, 82--83, 310, 312
Control group
In an experimental study or clinical trial, a group of subjects closely resembling the experimental group that serves as a baseline comparison when the results are evaluated, 338, 509--510
Correlation
A relationship in which things or events are frequently or always found to go together, 338--340
Diminishing marginal value
The principle that as quantity increases, relative value tends to decrease, 346--347
Double-blind study
A experimental study in which neither the subjects nor the researchers that work directly with the subjects know which subjects are members of the experimental group and which are members of the control group, 338, 509
Epistemic probability
The kind of probability we assign to statements we may have good reason to believe but to which we cannot assign a probability on any truly mathematical basis, 342
Expected value
The payoff or loss you can expect from making a bet, 345--347
Experimental group
In an experimental study, the group of subjects that receives the active medication or treatment being studied, 338, 509--510
Gambler's fallacy
The mistaken belief that a past event has an impact on a current random event, 344
Hasty generalization
A fallacy that occurs when an arguer draws a general conclusion (i.e., a conclusion of the form "All A's are B's" or "Most A's are B's") from a sample that is biased or too small, 172--173, 188, 310
Indicator words
Words or phrases that provide clues when a premise or conclusion is being offered, 29-31, 306
Inductive argument
An argument in which the conclusion is claimed or intended to follow probably from the premises, 52-62, 67-71, 83, 94, 305; common patterns of, 67-71
Inductive generalization
An argument that uses evidence about a limited number of people or things of a certain type to make a claim about a larger group of people or things of that type, 67--68, 71, 306--317; evaluating, 309--312; and opinion polls, 313--317
Law of large numbers
A statistical principle, according to which the proximity of theoretically predicted and actual percentages tends to increase as the sample size grows, 344-345
Placebo
A sugar pill or other inactive substance, often used in controlled experiments to determine the effectiveness of a treatment or drug, 338, 509
Placebo effect
An improvement or other change in a patient's condition produced by an inactive substance and thus due to the expectations of the patient rather than to any active treatment or medication the patient may be receiving, 338, 509
Population as a whole
The larger set of members from which a sample is drawn, 306
Questionable cause
A fallacy that occurs when an arguer claims without sufficient evidence that one thing is the cause of something else, 171--172, 334--335
Reference class
In statistics, the group to which one's statistics apply, 320--321
Relative frequency probability
The kind of probability that takes information about a group as a whole and applies it to an individual case based on accumulated data derived from what has already been observed in the group, 342
Relative value
The value a bet has in relation to an individual's own needs, preferences, and resources, 346--347
Reliable argument
An inductive argument that is strong and such that a rational person would rely upon it in practical decision-making, 319. See also Strong and reliable argument
Representative sample
A set of observed cases that accurately reflects relevant characteristics of the population as a whole, 311--312
Sample population
The set of members (selected from the population as a whole) that has been studied or observed, 306
Sound argument
A deductive argument that is valid and has all true premises, 78, 83, 95, 310
Statistical argument
An argument that argues from premises regarding a percentage of a population to a conclusion about an individual member of that population or some part of that population, 67, 70--71, 317--321
Strict necessity test
A test for determining whether an argument is deductive or inductive. According to the strict necessity test, if the conclusion of an argument follows from the premises with strict logical necessity, then the argument should be regarded as deductive, 56--58, 305; exceptions to, 61, 94
Strong argument
An inductive argument in which the conclusion follows probably from the premises, 78--83, 95, 305
Strong and reliable argument
An inductive argument in which the conclusion follows probably from the premises and is such that a reasonable person would rely upon it in practical matters, 319, 321
Strong and unreliable argument
An inductive argument in which the conclusion follows probably from the premises but is not such that a reasonable person would rely upon it in practical matters, 319, 312
Uncogent argument
An inductive argument that is weak or has at least one false premise, or both, 82-83, 310, 312
Unreliable argument
An inductive argument such that a reasonable person would not rely upon it in practical decision-making, 319
Unsound argument
A deductive argument that is invalid or has at least one false premise, or both, 78, 83, 310, 312
Weak analogy
A fallacy that occurs when an arguer's conclusion depends on a comparison of things that aren't relevantly similar, 175--177, 188, 326
Weak argument
An inductive argument in which the conclusion does not follow probably from the premises, 79, 83, 305, 312
