Illicit major is a
formal fallacy In philosophy, a formal fallacy, deductive fallacy, logical fallacy or non sequitur (; Latin for " tdoes not follow") is a pattern of reasoning rendered invalid by a flaw in its logical structure that can neatly be expressed in a standard logic s ...
committed in a
categorical syllogism
A syllogism ( grc-gre, συλλογισμός, ''syllogismos'', 'conclusion, inference') is a kind of logical argument that applies deductive reasoning to arrive at a conclusion based on two propositions that are asserted or assumed to be true.
...
that is
invalid
Invalid may refer to:
* Patient, a sick person
* one who is confined to home or bed because of illness, disability or injury (sometimes considered a politically incorrect term)
* .invalid, a top-level Internet domain not intended for real use
As t ...
because its
major term
A syllogism ( grc-gre, συλλογισμός, ''syllogismos'', 'conclusion, inference') is a kind of logical argument that applies deductive reasoning to arrive at a conclusion based on two propositions that are asserted or assumed to be true.
...
is
undistributed in the major premise but distributed in the conclusion.
This fallacy has the following argument form:
#''All A are B''
#''No C are A''
#''Therefore, no C are B''
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.
However, an argument in the following form differs from the above, and is valid (Camestres):
#''All A are B''
#''No B are C''
#''Therefore, no C are A''
See also
*
Illicit minor
Illicit minor is a formal 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.
: ...
*
Syllogistic fallacy
External links
Illicit MajorThe Fallacy Files
Syllogistic fallacies
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