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In philosophy
Philosophical logic

Philosophical logic is the study of the more specifically philosophical aspects of logic. The term contrasts with philosophy of logic, metalogic, and mathematical logic; and since the development of mathematical logic in the late nineteenth century, it has come to include most of those topics traditionally treated by logic in gene...
, a formal fallacy or a logical fallacy is a pattern of reasoning which is always wrong. This is due to a flaw in the structure of the argument which renders the argument invalid
Validity

The term Validity in logic applies to Argument or statements....
. A formal fallacy is contrasted with an informal fallacy
Informal fallacy

An informal fallacy is an Logical argument whose stated premises fail to support their proposed conclusion. The deviation in an informal fallacy often stems from a flaw in the path of reasoning that links the premises to the conclusion....
, which may have a valid logical form, but be false due to the characteristics of its premise
Premise

Premise can refer to:* Premise, a claim that is a reason for, or an objection against, some other claim as part of an argument* Premises, land and buildings together considered as a property...
s, or its justification structure.

The term fallacy
Fallacy

A fallacy is an argument which may convince some people but is not logically sound. Note that the truth of the conclusions of an argument does not determine whether the argument is a fallacy - it is the argument which is incorrect....
 is often used more generally to mean an argument which is problematic for any reason, whether it be a formal or an informal fallacy.

The presence of a formal fallacy in a deductive argument does not imply anything about the argument's premises or its conclusion.






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In philosophy
Philosophical logic

Philosophical logic is the study of the more specifically philosophical aspects of logic. The term contrasts with philosophy of logic, metalogic, and mathematical logic; and since the development of mathematical logic in the late nineteenth century, it has come to include most of those topics traditionally treated by logic in gene...
, a formal fallacy or a logical fallacy is a pattern of reasoning which is always wrong. This is due to a flaw in the structure of the argument which renders the argument invalid
Validity

The term Validity in logic applies to Argument or statements....
. A formal fallacy is contrasted with an informal fallacy
Informal fallacy

An informal fallacy is an Logical argument whose stated premises fail to support their proposed conclusion. The deviation in an informal fallacy often stems from a flaw in the path of reasoning that links the premises to the conclusion....
, which may have a valid logical form, but be false due to the characteristics of its premise
Premise

Premise can refer to:* Premise, a claim that is a reason for, or an objection against, some other claim as part of an argument* Premises, land and buildings together considered as a property...
s, or its justification structure.

The term fallacy
Fallacy

A fallacy is an argument which may convince some people but is not logically sound. Note that the truth of the conclusions of an argument does not determine whether the argument is a fallacy - it is the argument which is incorrect....
 is often used more generally to mean an argument which is problematic for any reason, whether it be a formal or an informal fallacy.

The presence of a formal fallacy in a deductive argument does not imply anything about the argument's premises or its conclusion. Both may actually be true, or even more probable as a result of the argument (e.g. appeal to authority
Appeal to authority

An appeal to authority or argument by authority is a type of Logical argument in logic. It bases the truth value of an assertion on the authority, knowledge, expertise, or position of the source asserting it....
), but the deductive argument is still invalid because the conclusion does not follow from the premises in the manner described. By extension, an argument can contain a formal fallacy even if the argument is not a deductive one; for instance an inductive argument that incorrectly applies principles of probability
Probability

Probability, or wikt:chance, is a way of expressing knowledge or belief that an Event will occur or has occurred. In mathematics the concept has been given an exact meaning in probability theory, that is used extensively in such areas of study as mathematics, statistics, finance, gambling, science, and philosophy to draw conclusions about t...
 or causality
Causality

Causality denotes a necessary relationship between one event and another event which is the direct consequence of the first.While this informal understanding suffices in everyday use, the Philosophy analysis of how best to characterize causality extends over millennia....
 can be said to commit a formal fallacy.

Recognizing fallacies in everyday arguments may be difficult since arguments are often embedded in rhetoric
Rhetoric

Rhetoric is the art of using language as a means to persuade. Along with logic and dialectic, rhetoric is one of the three ancient arts of discourse....
al patterns that obscure the logical connections between statements. Informal fallacies may also exploit the emotion
Emotion

An emotion is a mental and physiological state associated with a wide variety of feelings, thoughts, and behavior.Emotions are subjective experiences, or experienced from an individual point of view....
s or intellectual or psychological
Psychology

Psychology is an academic and applied science discipline involving the science study of human mental functions and behavior. Occasionally it also relies on symbolic hermeneutics and critical theory, although these traditions are less pronounced than in other social sciences such as sociology....
 weaknesses of the audience. Having the capability to recognize fallacies in arguments is one way to reduce the likelihood of such occurrences.

A different approach to understanding and classifying fallacies is provided by argumentation theory
Argumentation theory

Argumentation theory, or argumentation, embraces the arts and sciences of civil debate, dialogue, conversation, and persuasion; studying rules of inference, logic, and procedural rules in both Artificial intelligence and real world settings....
. In this approach, an argument is regarded as an interactive protocol
Protocol (diplomacy)

In international politics, protocol is the etiquette of diplomacy and affairs of state.A protocol is a wiktionary:rule which guides how an activity should be performed, especially in the field of diplomacy....
 between individuals which attempts to resolve their disagreements. The protocol is regulated by certain rules of interaction and violations of these rules are fallacies. Many of the fallacies in the list below are best understood as being fallacies in this sense.

Such fallacies are used in many forms of modern communications where the intention is to influence behavior and change beliefs - examples in the mass media
Mass media

Mass media is a term used to denote a section of the media specifically envisioned and designed to reach a mainstream such as the population of a nation state....
 today include but are not limited to propaganda
Propaganda

Propaganda is the dissemination of information aimed at influencing the opinions or behaviors of large numbers of people. As opposed to Objectivity providing information, propaganda in its most basic sense presents information in order to influence its audience....
, advertisements, politics
Politics

Politics is the process by which groups of people make decisions. The term is generally applied to behaviour within civil governments, but politics has been observed in all human group interactions, including corporation, academia, and religion institutions....
, newspaper editorials and opinion-based news shows.

Common examples


For a list of types of formal and informal fallacy, as well as examples of fallacious arguments, see Fallacy
Fallacy

A fallacy is an argument which may convince some people but is not logically sound. Note that the truth of the conclusions of an argument does not determine whether the argument is a fallacy - it is the argument which is incorrect....
. For a concise list of "appeal to" fallacies, see Appeal (disambiguation)
Appeal (disambiguation)

Appeal may refer to:* Appeal – in law an appeal is a challenge of a judicial judgement to a higher authority, usually called an appellate court....
.

See also

  • Anecdotal evidence
    Anecdotal evidence

    The expression anecdotal evidence has two distinct meanings. Evidence in the form of an anecdote or hearsay is called anecdotal if there is doubt about its veracity: the evidence itself is considered untrustworthy or untrue....
  • Apophasis
    Apophasis

    Apophasis refers, in general, to "mentioning by not mentioning". Apophasis covers a wide variety of figures of speech....
  • Bandwagon fallacy
    Argumentum ad populum

    An argumentum ad populum , in logic, is a logical fallacy that concludes a proposition to be true because many or all people believe it; it alleges that "If many believe so, it is so."...
  • Cogency
    Cogency

    An logical argument is cogent if and only if the truth of the argument's premises would render the truth of the conclusion probable , and the argument's premises are, in fact, true....
  • Cognitive bias
    Cognitive bias

    A cognitive bias is a person's tendency to make errors in judgment based on cognitive factors, and is a phenomenon studied in cognitive science and social psychology....
  • Conjunction fallacy
    Conjunction fallacy

    The conjunction fallacy is a logical fallacy that occurs when it is assumed that specific conditions are more probable than a single general one....
  • Demagogy
    Demagogy

    Demagogy refers to a political strategy for gaining political power by appealing to the popular prejudices, emotions, fears and expectations of the public ? typically via impassioned rhetoric and propaganda, and often using Nationalism or Populism themes....
  • Fallacy
    Fallacy

    A fallacy is an argument which may convince some people but is not logically sound. Note that the truth of the conclusions of an argument does not determine whether the argument is a fallacy - it is the argument which is incorrect....
  • Fallacies of definition
    Fallacies of definition

    Fallacies of definition refer to the various ways in which definitions can fail to have merit. The term is used to suggest analogy with the formal fallacy....
  • False statement
    False statement

    A false statement is a statement that can be either willfully or unknowingly untrue. Though "fallacy" is often used as a synonym for "false statement" this is not logical fallacy or most formal contexts....
  • Informal logic
    Informal logic

    The precise nature and definition of informal logic are matters of some dispute. Ralph Johnson and J. Anthony Blair define informal logic as "a branch of logic whose task is to develop non-formal standards, criteria, procedures for the analysis, interpretation, evaluation, criticism and construction of argumentation." This definition reflects what...
  • Invalid proof
    Invalid proof

    In mathematics, there are a variety of spurious Mathematical proof of obvious contradictions. Although the proofs are flawed, the errors, usually by design, are comparatively subtle....
  • Paradox
    Paradox

    A paradox is a Proposition or group of statements that leads to a contradiction or a situation which defies intuition ; or, it can be an apparent contradiction that actually expresses a non-dual truth ....
  • Sophism
    Sophism

    Sophism can mean two very different things: In the modern definition, a sophism is a confusing or illogical argument used for deceiving someone....
  • Soundness
    Soundness

    In mathematical logic, a logical system has the soundness property if and only if its inference rules prove only formula that are valid with respect to its semantics....
  • Spurious relationship
    Spurious relationship

    In statistics, a spurious relationship is a mathematical relationship in which two occurrences have no causal connection, yet it may be inferred that they do, due to a certain third, unseen factor ....
  • Validity
    Validity

    The term Validity in logic applies to Argument or statements....
  • Vacuous truth
    Vacuous truth

    A vacuous truth is a truth that is devoid of content because it asserts something about all members of a class that is empty or because it says "If A then B" when in fact A is false....


External links

by — real examples posted regularly. Bruce Thompson's Ten common fallacies in an interactive test format. is a collection of one-off fallacies coined for specific, rhetorical purposes.