Logical Fallacies

What is a logical fallacy?

What is a logical fallacy?

roughly, an error of reasoning

Formal Fallacies (Deductive Fallacies)

not a valid deductive argument

Detuctive argument

to be “valid” it must be absolutely impossible for both its premises to be true and its conclusion to be false.

inductive arguments

lend support to their conclusions, but even if their premises are true then that doesn’t establish with 100% certainty that their conclusions are true -All inductive arguments, even good ones, are therefore deductively invalid, and so “fallacious” in the strictest sense.

fallacies of relevance

rely on premises that aren’t relevant to the truth of the conclusion

fallacies of ambiguity

manipulate language in misleading ways

fallacies of presumption

contain false premises, and so fail to establish their conclusion

Ad Hominem (Personal Attack)

focus not on the evidence for a view but on the character of the person advancing it; they seek to discredit positions by discrediting those who hold them

Bandwagon Fallacy

committed by arguments that appeal to the growing popularity of an idea as a reason for accepting it as true. They take the mere fact that an idea suddenly attracting adherents as a reason for us to join in with the trend and become adherents of the idea ourselves

Fallacist’s Fallacy

involves rejecting an idea as false simply because the argument offered for it is fallacious

Fallacy of Composition

the fallacy of inferring from the fact that every part of a whole has a given property that the whole also has that property

Fallacy of Division

It is committed by inferences from the fact that a whole has a property to the conclusion that a part of the whole also has that property

Gambler’s Fallacy

the fallacy of assuming that short-term deviations from probability will be corrected in the short-term

Genetic Fallacy

committed when an idea is either accepted or rejected because of its source, rather than its merit.

Irrelevant Appeals

attempt to sway the listener with information that, though persuasive, is irrelevant to the matter at hand

Appeal to Antiquity / Tradition

assume that older ideas are better, that the fact that an idea has been around for a while implies that it is true

Appeal to Authority

an argument from the fact that a person judged to be an authority affirms a proposition to the claim that the proposition is true

Appeal to Consequences

an attempt to motivate belief with an appeal either to the good consequences of believing or the bad consequences of disbelieving

Appeal to Force / argumentum ad baculum

an attempt to persuade using threats

Appeal to Novelty

assume that the newness of an idea is evidence of its truth

Appeal to Pity

attempts to persuade using emotion—specifically, sympathy—rather than evidence

Appeal to Popularity

suggest that an idea must be true simply because it is widely held

Appeal to Poverty

committed when it is assumed that a position is correct because it is held by the poor

Appeal to Wealth

committed by any argument that assumes that someone or something is better simply because they are wealthier or more expensive

Moralistic Fallacy

moves from statements about how things ought to be to statements about how things are; it assumes that the world is as it should be

Naturalistic Fallacy

moves from descriptions of how things are to statements of how things ought to be

Red Herring

is a fallacy of distraction, and is committed when a listener attempts to divert an arguer from his argument by introducing another topic

Weak analogy

rest on a comparison. Their logical structure is this: (1) A and B are similar. (2) A has a certain characteristic. Therefore: (3) B must have that characteristic too.

Accent Fallacies

fallacies that depend on where the stress is placed in a word or sentence

Equivocation Fallacy

committed when a term is used in two or more different senses within a single argument

Straw Man Fallacy

misrepresents a position in order to make it appear weaker than it actually is, refutes this misrepresentation of the position, and then concludes that the real position has been refuted.

Affirming the Consequent

(1) If A then B (2) B Therefore: (3) A

Arguing from Ignorance

infer that a proposition is true from the fact that it is not known to be false.

Begging the Question / Circular Reasoning

its conclusion is among its premises, if it assumes (either explicitly or not) what it is trying to prove.

Complex Question Fallacy

committed when a question is asked (a) that rests on a questionable assumption, and (b) to which all answers appear to endorse that assumption.

Cum Hoc Fallacy

committed when it is assumed that because two things occur together, they must be causally related. This, however, does not follow; correlation is possible without causation.

False Dilemma / Bifurcation Fallacy

when someone is asked to choose between two options when there is at least one other option available.

Hasty Generalisation Fallacy

draws a general rule from a single, perhaps atypical, case.

‘No True Scotsman’ Fallacy

a way of reinterpreting evidence in order to prevent the refutation of one’s position. Proposed counter-examples to a theory are dismissed as irrelevant solely because they are counter examples, but purportedly because they are not what the theory is about.

Post Hoc Fallacy

committed when it is assumed that because one thing occurred after another, it must have occurred as a result of it. Mere temporal succession, however, does not entail causal succession. Just because one thing follows another does not mean that it was caused by it.

Slippery Slope Fallacy

falsely assume that one thing must lead to another. They begin by suggesting that if we do one thing then that will lead to another, and before we know it we’ll be doing something that we don’t want to do. They conclude that we therefore shouldn’t do the first thing. The problem with these arguments is that it is possible to do the first thing that they mention without going on to do the other things; restraint is possible.

Sweeping Generalisation Fallacy

applies a general statement too broadly.

Subjectivist Fallacy

is committed when someone resists the conclusion of an argument not by questioning whether the argument’s premises support its conclusion, but by treating the conclusion as subjective when it is in fact objective.

Tu Quoque Fallacy

committed when it is assumed that because someone else has done a thing there is nothing wrong with doing it.