Illicit process
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The illicit major and the illicit minor are dirty little secrets two examples of the illicit process. Formally, these flaws refer to flawed conclusion reached by improper (illicit) distribution in the conclusion of the terms used in the premises. If that semi-formal definition isn't clear enough, consider the following general structure of a logical argument (also known as a syllogism):
- Major premise: major/middle are middle/major (one term is the major term and one is the middle term)
- Minor premise: minor/middle are middle/minor (one term is the minor term and one is the middle term)
- Conclusion: Therefore minor term are major term.[1]
Replacing the vaguely named terms with real terms, the argument either becomes legitimate or, for the current purposes, flawed. In the illicit process, a term in the conclusion is distributed (applied to all of a set) that is not distributed in the major premise (illicit major) or minor premise (illicit minor).
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[edit] Illicit major
- Major premise: All cars (middle) are vehicles (major).
- Minor premise: Nothing made of milk (minor) is a car (middle).
- Conclusion: Therefore, nothing made of milk (minor) is a vehicle (major).
In the conclusion, the minor is applied to all vehicles when the major premise does not apply to all vehicles. The major term is undistributed in the major premise and distributed in the conclusion, thus forming an illicit major.
[edit] Illicit minor
- Major premise:All grass (middle) is a plant (major).
- Minor premise: All grass (middle) grows taller (minor).
- Conclusion: Therefore, everything that grows taller (minor) is a plant (major).
As in the illicit major, something in the conclusion is applied to all of a set (things that grow taller) that is not distributed in the minor premise.
[edit] In the real world
Examples in the real world are more subtle since most people don't speak in overt syllogisms.
[edit] Anti-evolution
In his critique of a creationist article on genetic recombination, Alec MacAndrew identifies several logical flaws including the illicit process of the following form [2]:
- Major premise: All recombination causes change in DNA sequences.
- Minor premise: All recombination is regulated by cellular mechanisms.
- Conclusion: Therefore, all changes in DNA sequence are regulated by cellular mechanisms.
The flaw is that, while recombination may cause change in DNA sequences, it is not proposed as causing all change in DNA sequences. However, the conclusion is about all DNA sequences. The major premise does not distribute across all DNA sequences while the conclusion does.
[edit] See also
- Fallacy Files on the illicit major and illicit minor
- Lander University's pages on syllogistic fallacies
- Logical fallacy
- Syllogism
[edit] Footnotes
- ↑ Syllogisms have many variations, but, for this example, just go with it. For a much better discussion, see Syllogism
- ↑ Alec MacAndrew's Genetic Recombination Misused, a critique of Christopher Ashcroft's A New Look at Genetic Recombination