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Information about Illicit Major

Illicit major is a logical fallacy committed in a categorical syllogism that is invalid because its major term is undistributed in the major premise but distributed in the conclusion.

Example:
  • All dogs are mammals.
  • No cats are dogs.
  • Therefore, no cats are mammals.
In this argument, the major term is "mammals". This is distributed in the conclusion (the last statement) because we are making a claim about a property of all mammals: that they are not cats. However, it is not distributed in the major premise (the first statement) where we are only talking about a property of some mammals: Only some mammals are dogs.

The error is in assuming that the converse of the first statement (that all mammals are dogs) is also true.

See also

This article was originally based on material from the Free On-line Dictionary of Philosophy, which is licensed under the GFDL.


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Formal fallacies
Argument from fallacy • Fallacy of modal logic • Masked man fallacy • Appeal to probability • Bare assertion fallacy
Fallacy of propositional logic:Affirming a disjunct • Affirming the consequent • Commutation of Conditionals • False dilemma • Denying the antecedent • Improper Transition
Fallacy of quantificational logic:Existential fallacy • Illicit Conversion • Quantifier shift • Unwarranted contrast
Syllogistic fallacy:Affirmative conclusion from a negative premise • Negative conclusion from an affirmative premise • Exclusive premises • Necessity • Four-term Fallacy • Illicit major • Illicit minor • Undistributed middle
A fallacy is a component of an argument that is demonstrably flawed in its logic or form, thus rendering the argument invalid in whole. In logical arguments, fallacies are either formal or informal.
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A syllogism (Greek: συλλογισμός — "conclusion," "inference"), (usually the categorical syllogism
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validity as it occurs in logic refers generally to a property of deductive arguments, although many logic texts apply the term to statements as well (a statement is a sentence that “has a truth value,” i.e., that is either true or false).
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The major term is the predicate term of the conclusion of a categorical syllogism. It appears in the major premise along with the middle term and not the minor term. It is an end term (meaning not the middle term).
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A categorical term is said to be distributed, if all individual members of that category are accounted for. In a statement like "All A are either B or C", the term A is distributed, because all elements of the set A are pinpointed.
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Illicit minor is a logical fallacy committed in a categorical syllogism that is invalid because its minor term is undistributed in the minor premise but distributed in the conclusion.

This fallacy has the following argument form:
All A are B.

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Syllogistic fallacies are logical fallacies that occur in syllogisms. They include:

Any syllogism type (other than polysyllogism and disjunctive):
  • fallacy of four terms
Occurring in categorical syllogisms:

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The Free On-line Dictionary of Philosophy (FOLDOP) is published by the SWIF and edited by Luciano Floridi and Gian Paolo Terravecchia. FOLDOP is a searchable dictionary of technical words, concepts, acronyms, ideas and theories from philosophy.
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GNU Free Documentation License (GNU FDL or simply GFDL) is a copyleft license for free documentation, designed by the Free Software Foundation (FSF) for the GNU project.
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In philosophy, 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.
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The argument from fallacy, also known as argumentum ad logicam or fallacy fallacy, is a logical fallacy which assumes that if an argument is fallacious, its conclusion must be false.

It has the general argument form:
If P, then Q.

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In formal logic, a modal logic is any logic for handling modalities: concepts like possibility, existence, and necessity. Logics for handling a number of other ideas, such as eventually, formerly, can, could
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The masked man fallacy is a fallacy of formal logic in which substitution of identical designators in a true statement can lead to a false one. The name comes from the example "I do not know who the masked man is", which can be true even though the masked man is Jones, and I know
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The appeal to probability is a logical fallacy, often used in conjunction with other fallacies. It assumes that because something could happen, it is inevitable that it will happen. This is flawed logic, regardless of the likelihood of the event in question.
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The bare assertion fallacy is fallacy in formal logic where a premise in an argument is assumed to be true merely because it says that it is true.

One form of the fallacy may be summarized as follows:
  • Fact 1: X claims statement A.

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In logic and mathematics, a propositional calculus (or a sentential calculus) is a formal system in which formulas representing propositions can be formed by combining atomic propositions using logical connectives, and a system of formal proof rules
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The logical fallacy of affirming a disjunct also known as the fallacy of the alternative disjunct occurs when a deductive argument takes either of the two following forms:

A or B
A
Therefore, it is not the case that B

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Affirming the consequent is a formal fallacy, committed by reasoning in the form:

If P, then Q.
Q.
Therefore, P.

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false dilemma—also known as false choice, false dichotomy, falsified dilemma, fallacy of the excluded middle, black and white thinking, false correlative, either/or fallacy, and bifurcation
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Denying the antecedent is a logical fallacy, committed by reasoning in the form:

If P, then Q.
Not P.
Therefore, not Q.

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The term quantification has several meanings, general and specific. Primarily it covers all those acts which quantify observations and experiences by converting them into numbers through counting and measuring. It is thus the basis for mathematics and for science.
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The existential fallacy, or existential instantiation, is a logical fallacy committed in a categorical syllogism that is invalid because it has two universal premises and a particular conclusion.
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An illicit conversion is the invalid inversion of a A- or O-type proposition. It can also be defined as an argument which entails the arbitrary assignment of a specific trait of a set to one of its subsets.
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Syllogistic fallacies are logical fallacies that occur in syllogisms. They include:

Any syllogism type (other than polysyllogism and disjunctive):
  • fallacy of four terms
Occurring in categorical syllogisms:

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Affirmative conclusion from a negative premise is a logical fallacy that is committed when a categorical syllogism has a positive conclusion, but one or two negative premises.

For example:
No fish are dogs, and no dogs can fly, therefore all fish can fly.

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The fallacy of exclusive premises is a formal fallacy committed in a categorical syllogism that is invalid because both of its premises are negative.

Example:

No mammals are fish.
Some fish are not whales.

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A fallacy of necessity is a fallacy in the logic of a syllogism whereby a degree of unwarranted necessity is placed in the conclusion.

Example:

a) ''Bachelors are necessarily unmarried.
b) John is a bachelor.

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The fallacy of four terms (Latin: quaternio terminorum) is the logical fallacy that occurs when a categorical syllogism has four terms.

Valid categorical syllogisms always have three terms:

Major premise: All fish have fins.

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Illicit minor is a logical fallacy committed in a categorical syllogism that is invalid because its minor term is undistributed in the minor premise but distributed in the conclusion.

This fallacy has the following argument form:
All A are B.

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The fallacy of the undistributed middle is a logical fallacy that is committed when the middle term in a categorical syllogism isn't distributed. It is thus a syllogistic fallacy.
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