https://teddyrookbook.com/logic/informal-logic/Recent content in Informal Logic on Teddy Rook Bookhttps://teddyrookbook.com/img/share.jpghttps://teddyrookbook.com/img/share.jpgHugoenhttps://teddyrookbook.com/logic/informal-logic/statements/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/statements/A statement is a sentence that is either true or false; questions, commands and exclamations are not statements. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/arguments/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/arguments/An argument offers reasons (premises) meant to support a claim (the conclusion); a report, description, warning or bare opinion does not. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/explanations/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/explanations/An argument tries to show that something is true; an explanation tells why something we already accept is true. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/premise-conclusion/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/premise-conclusion/Find the conclusion first by asking what the speaker wants you to believe; the premises are the reasons given for it. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/indicator-words/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/indicator-words/Words like "therefore" and "so" usually mark a conclusion; "because", "since" and "for" usually mark a premise. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/standard-form/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/standard-form/Rewrite an argument as numbered premises followed by its conclusion, leaving out filler, repeats and side remarks. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/argument-maps/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/argument-maps/Linked premises support the conclusion only together; convergent premises each give a separate reason on their own. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/subarguments/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/subarguments/A claim can be the conclusion of one step and a premise of the next; the last claim supported is the main conclusion. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/unstated-premises/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/unstated-premises/Many arguments leave a premise unsaid; supply the most reasonable one that connects the stated premises to the conclusion. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/deductive-inductive/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/deductive-inductive/A deductive argument claims its conclusion must be true if the premises are; an inductive argument claims only that it is probably true. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/validity/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/validity/An argument is valid when it is impossible for all its premises to be true and its conclusion false. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/counterexample-method/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/counterexample-method/To show a form is invalid, give an argument with the same form whose premises are plainly true and whose conclusion is plainly false. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/soundness/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/soundness/A sound argument is valid and has all true premises, so its conclusion must be true. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/validity-truth-combos/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/validity-truth-combos/Every mix of true and false premises and conclusions is possible for a valid argument except one: true premises with a false conclusion. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/inductive-strength/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/inductive-strength/An inductive argument is strong when its premises, if true, make the conclusion likely; a strong argument with true premises is cogent. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/generalizations/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/generalizations/A generalization is only as good as its sample: large enough, chosen fairly, and like the whole group in the ways that matter. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/analogies/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/analogies/An analogy argues that two things alike in some ways are alike in another; it is strong when the likenesses are relevant and the differences are not. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/causal-reasoning/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/causal-reasoning/Two things happening together does not show that one causes the other; look for a common cause, reverse direction, or coincidence. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/ambiguity-vagueness/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/ambiguity-vagueness/A word is ambiguous when it has two distinct meanings in context, and vague when its boundary is fuzzy. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/kinds-of-definitions/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/kinds-of-definitions/Lexical definitions report how a word is used, stipulative ones assign a new meaning, precising ones sharpen a vague word, and persuasive ones slant it. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/genus-difference/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/genus-difference/A classical definition names the larger kind (genus) and the feature that sets this thing apart within it (difference). Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/definition-rules/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/definition-rules/A good definition is neither too broad nor too narrow, not circular, not negative when it can be positive, and not figurative or obscure. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/loaded-language/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/loaded-language/Words can carry feelings as well as facts; loaded words try to win agreement by attitude instead of by reasons. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/verbal-disputes/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/verbal-disputes/Some disagreements are about the facts; others vanish once people notice they are using a word in different senses. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/fallacy-intro/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/fallacy-intro/A fallacy is a common pattern of bad reasoning that can look persuasive; formal fallacies are flaws in form, informal ones in content. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/ad-hominem/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/ad-hominem/Ad hominem rejects a claim by attacking the person who made it (insults or their circumstances) instead of the reasons given. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/tu-quoque/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/tu-quoque/Tu quoque dismisses an argument because the arguer does not follow their own advice. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/straw-man/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/straw-man/A straw man swaps the opponent's real position for a weaker or exaggerated version, then knocks that down. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/red-herring/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/red-herring/A red herring changes the subject to a different issue, then treats the original question as settled. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/appeal-to-force/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/appeal-to-force/An appeal to force tries to win agreement by a threat of harm instead of by reasons. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/appeal-to-pity/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/appeal-to-pity/An appeal to pity asks us to accept a claim because of sympathy, when the sympathy has no bearing on whether the claim is true. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/appeal-to-popularity/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/appeal-to-popularity/The bandwagon fallacy argues that a claim is true, or a choice good, because many people believe it or do it. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/appeal-to-authority/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/appeal-to-authority/Citing an expert in their own field, where experts agree, is reasonable; citing someone outside their expertise, or one voice against a consensus, is not. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/appeal-to-ignorance/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/appeal-to-ignorance/An appeal to ignorance argues that a claim is true because it has not been shown false, or false because it has not been shown true. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/begging-question/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/begging-question/An argument begs the question when a premise assumes the very conclusion it is supposed to prove, often in other words. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/complex-question/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/complex-question/A complex question has a hidden assumption built in, so that any direct answer grants it. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/false-dilemma/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/false-dilemma/A false dilemma presents two options as the only ones when others exist. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/hasty-generalization/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/hasty-generalization/A hasty generalization draws a conclusion about a whole group from a sample that is too small or not typical. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/false-cause/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/false-cause/False cause claims one thing caused another only because it came first (post hoc) or because the two occur together. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/slippery-slope/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/slippery-slope/A slippery slope claims one step will set off a chain of bad results, without good reason to think each link will happen. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/weak-analogy/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/weak-analogy/A weak analogy rests on likenesses that do not matter for the conclusion, or ignores differences that do. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/suppressed-evidence/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/suppressed-evidence/Suppressed evidence leaves out an important fact that would change the conclusion. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/accident/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/accident/Accident applies a general rule to a special case that the rule was never meant to cover. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/equivocation/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/equivocation/Equivocation uses a word in one sense in one premise and in another sense elsewhere, so the argument only seems to connect. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/amphiboly/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/amphiboly/Amphiboly draws a conclusion from a sentence whose grammar allows two readings. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/composition/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/composition/Composition reasons that because every part has a property, the whole must have it too. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/division/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/division/Division reasons that because the whole has a property, each part must have it too. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/conditional-fallacies/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/conditional-fallacies/From "if P then Q", you may infer Q from P, and not-P from not-Q; inferring P from Q, or not-Q from not-P, is a fallacy. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/telling-apart/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/telling-apart/Name the fallacy by the job the faulty step does: distorting a view, changing the subject, leaping from a sample, or assuming the conclusion. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/fallacy-or-not/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/fallacy-or-not/Many fallacy names have fair cousins: trusted experts, well-supported chains of causes, and real either-or choices are good reasoning. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/charity/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/charity/Before judging an argument, state it in its strongest reasonable form, the way its author would accept. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/evaluate-argument/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/evaluate-argument/Find the conclusion and premises, check whether the reasoning is valid or strong, then check whether the premises are true. Informal Logic · Logic Ladderhttps://teddyrookbook.com/logic/informal-logic/objections/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/logic/informal-logic/objections/A strong case answers the best objection to it; an objection attacks a premise or the link from premises to conclusion. Informal Logic · Logic Ladder