Formal / Deductive Fallacy
A pattern of reasoning rendered invalid by a flaw in its logical structure that can neatly be expressed in a standard logic system. The conclusion does not follow from the premises in the manner described.
A deductive fallacy is a deductive argument that
Informal / Inductive Fallacy
An inductive fallacy is less formal than a deductive fallacy. They are simply "arguments" which appear to be inductive arguments, but the premises do not provided enough support for the conclusion. In such cases, even if the premises were true, the conclu
Argument
an argument consists of one or more premises and one conclusion. A premise is a statement (a sentence that is either true or false) that is offered in support of the claim being made, which is the conclusion (which is also a sentence that is either true o
Inductive Argument
An inductive argument is an argument such that the premises provide (or appear to provide) some degree of support (but less than complete support) for the conclusion.
A good inductive argument is known as a strong (or "cogent") inductive argument. It is s
Deductive Argument
A deductive argument is an argument such that the premises provide (or appear to provide) complete support for the conclusion.
A good deductive argument is known as a valid argument and is such that if all its premises are true, then its conclusion must b
Fallacy
A fallacy is, very generally, an error in reasoning. This differs from a factual error, which is simply being wrong about the facts. To be more specific, a fallacy is an "argument" in which the premises given for the conclusion do not provide the needed d
Fallacies of Relevance
Arguments that commit fallacies of relevance rely on premises that aren't relevant to the truth of the conclusion. The various irrelevant appeals are all fallacies of relevance, as are ad hominems.
Fallacies of Ambiguity
Arguments that commit fallacies of ambiguity, such as equivocation or the straw man fallacy, manipulate language in misleading ways
Fallacies of Presumption
Arguments that commit fallacies of presumption contain false premises, and so fail to establish their conclusion. For example, arguments based on a false dilemma or circular arguments both commit fallacies of presumption.
Ad Hominem (Personal Attack)
It is important to note that the label "ad hominem" is ambiguous, and that not every kind of ad hominem argument is fallacious. In one sense, an ad hominem argument is an argument in which you offer premises that you the arguer don't accept, but which you
Bandwagon Fallacy
The bandwagon fallacy is 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 beco
Fallacist's Fallacy
The fallacist's fallacy involves rejecting an idea as false simply because the argument offered for it is fallacious. Having examined the case for a particular point of view, and found it wanting, it can be tempting to conclude that the point of view is f
Fallacy of Composition
The fallacy of composition is the fallacy of inferring from the fact that every part of a whole has a given property that the whole also has that property. This pattern of argument is the reverse of that of the fallacy of division. It is not always fallac
Fallacy of Division
The fallacy of division is the reverse of the fallacy of composition. 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. Like the fallacy of composition, this is only
Gambler's Fallacy
Belief that independent phenomena are subject to statistical "runs"
The gambler's fallacy is the fallacy of assuming that short-term deviations from probability will be corrected in the short-term. Faced with a series of events that are statistically unli
Genetic Fallacy
The genetic fallacy is committed when an idea is either accepted or rejected because of its source, rather than its merit.
Even from bad things, good may come; we therefore ought not to reject an idea just because of where it comes from, as ad hominem arg
Irrelevant Appeals
Irrelevant appeals attempt to sway the listener with information that, though persuasive, is irrelevant to the matter at hand. There are many different types of irrelevant appeal, many different ways of influencing what people think without using evidence
Appeal to Antiquity/Tradition
An appeal to antiquity is the opposite of an appeal to novelty. Appeals to antiquity assume that older ideas are better, that the fact that an idea has been around for a while implies that it is true. This, of course, is not the case; old ideas can be bad
Appeal to Authority
Something is right/good/correct because an authority figure said so.
An appeal to authority is an argument from the fact that a person judged to be an authority affirms a proposition to the claim that the proposition is true.
Appeals to authority are alwa
Appeal to Consequences
Argument from the consequence of something
An appeal to consequences is an attempt to motivate belief with an appeal either to the good consequences of believing or the bad consequences of disbelieving. This may or may not involve an appeal to force. Such
Appeal to Force
An appeal to force is an attempt to persuade using threats. Its Latin name, "argumentum ad baculum", literally means "argument with a cudgel". Disbelief, such arguments go, will be met with sanctions, perhaps physical abuse; therefore, you'd better believ
Appeal to Novelty
An appeal to novelty is the opposite of an appeal to antiquity. Appeals to novelty assume that the newness of an idea is evidence of its truth. They are thus also related to the bandwagon fallacy.
That an idea is new certainly doesn't entail that it is tr
Appeal to Pity
An appeal to pity attempts to persuade using emotion�specifically, sympathy�rather than evidence. Playing on the pity that someone feels for an individual or group can certainly affect what that person thinks about the group; this is a highly effective, a
Appeal to Popularity
Appeals to popularity suggest that an idea must be true simply because it is widely held. This is a fallacy because popular opinion can be, and quite often is, mistaken. Hindsight makes this clear: there were times when the majority of the population beli
Appeal to Poverty
The appeal to poverty fallacy is committed when it is assumed that a position is correct because it is held by the poor. The opposite of the appeal to poverty is the appeal to wealth.
There is sometimes a temptation to contrast the excesses, greed, and im
Appeal to Wealth
The appeal to wealth fallacy is committed by any argument that assumes that someone or something is better simply because they are wealthier or more expensive. It is the opposite of the appeal to poverty.
In a society in which we often aspire to wealth, w
Moralistic Fallacy
The moralistic fallacy is the opposite of the naturalistic fallacy. The naturalistic fallacy moves from descriptions of how things are to statements of how things ought to be, the moralistic fallacy does the reverse. The moralistic fallacy moves from stat
Naturalistic Fallacy
There are two fundamentally different types of statement: statements of fact which describe the way that the world is, and statements of value which describe the way that the world ought to be. The naturalistic fallacy is the alleged fallacy of inferring
Red Herring
The red herring is as much a debate tactic as it is a logical fallacy. It is a fallacy of distraction, and is committed when a listener attempts to divert an arguer from his argument by introducing another topic. This can be one of the most frustrating, a
Weak Analogy
Arguments by 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.
For example, William Paley's argument from design suggests that a
Fallacies of Ambiguity (Types)
Accent Fallacies
Equivocation Fallacies
Straw Man Fallacy
Accent Fallacies
Accent fallacies are fallacies that depend on where the stress is placed in a word or sentence. The meaning of a set of words may be dramatically changed by the way they are spoken, without changing any of the words themselves. Accent fallacies are a type
Equivocation Fallacy
The fallacy of equivocation is committed when a term is used in two or more different senses within a single argument.
For an argument to work, words must have the same meaning each time they appear in its premises or conclusion. Arguments that switch bet
Straw Man Fallacy
A straw man argument is one that 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. This, of course, is a fallacy, bec
Fallacies of Presumption (Types)
- Affirming the Consequent
- Arguing from Ignorance
- Begging the question / circular reasoning
- Complex question fallacy
- Cum Hoc Fallacy
- False dilemma / bifurcation fallacy
- Hasty generalization fallacy
- No True Scotsman Fallacy
- Post Hoc Fallacy
Affirming the Consequent
The fallacy of affirming the consequent is committed by arguments that have the form:
(1) If A then B
(2) B
Therefore:
(3) A
The first premise of such arguments notes that if a state of affairs A obtained then a consequence B would also obtain. The second
Arguing from Ignorance
Arguments from ignorance infer that a proposition is true from the fact that it is not known to be false. Not all arguments of this form are fallacious; if it is known that if the proposition were not true then it would have been disproven, then a valid a
Begging the Question / Circular Reasoning
An argument is circular if its conclusion is among its premises, if it assumes (either explicitly or not) what it is trying to prove. Such arguments are said to beg the question. A circular argument fails as a proof because it will only be judged to be so
Complex Question
The complex question fallacy is committed when a question is asked (a) that rests on a questionable assumption, and (b) to which all answers appear to endorse that assumption.
Examples
"Have you stopped beating your wife?"
This is a complex question becau
Cum Hoc Fallacy
The complex question fallacy is committed when a question is asked (a) that rests on a questionable assumption, and (b) to which all answers appear to endorse that assumption.
Examples
"Have you stopped beating your wife?"
This is a complex question becau
False Dilemma / Bifurcation Fallacy
The bifurcation fallacy is committed when a false dilemma is presented, i.e. when someone is asked to choose between two options when there is at least one other option available. Of course, arguments that restrict the options to more than two but less th
Hasty Generalization
A hasty generalisation draws a general rule from a single, perhaps atypical, case. It is the reverse of a sweeping generalisation.
Example
(1) My Christian / atheist neighbour is a real grouch.
Therefore:
(2) Christians / atheists are grouches.
This argum
No True Scotsman Fallacy
The no true scotsman fallacy is 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
Post Hoc Fallacy
The Latin phrase "post hoc ergo propter hoc" means, literally, "after this therefore because of this." The post hoc fallacy is committed when it is assumed that because one thing occurred after another, it must have occurred as a result of it. Mere tempor
Slippery Slope
Slippery slope arguments 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 th
Sweeping Generalization Fallacy
A sweeping generalisation applies a general statement too broadly. If one takes a general rule, and applies it to a case to which, due to the specific features of the case, the rule does not apply, then one commits the sweeping generalisation fallacy. Thi
Subjectivist Fallacy
There are two types of claim: objective and subjective.
Objective claims have the same truth-value for everyone. For example, the claim that the Earth is cuboid is an objective claim; it's either true for everyone or false for everyone. It isn't possible
Tu Quoquo Fallacy
There are two types of claim: objective and subjective.
Objective claims have the same truth-value for everyone. For example, the claim that the Earth is cuboid is an objective claim; it's either true for everyone or false for everyone. It isn't possible