Illicit Process

Taxonomy: Logical Fallacy > Formal Fallacy > Syllogistic Fallacy > Illicit Process



Any form of categorical syllogism in which a term that is distributed in the conclusion is undistributed in a premiss.

Syllogistic Rule Violated:

In a validating form of categorical syllogism, any term that is distributed in the conclusion is distributed in the premiss in which it occurs.


An argument with a term distributed in the conclusion, but not in its premiss, commits a fallacy of illicit process. Since every categorical proposition has two terms, this means that there are two subfallacies of this fallacy―see above―depending upon whether it is the major term or the minor term which is illicitly distributed. Every categorical syllogism that commits the fallacy of illicit process also commits at least one of its subfallacies, depending on which term is distributed in the conclusion. Some forms of categorical syllogism have both an illicit major and minor terms, but arguments with these forms are so implausible that it's unlikely anyone would be fooled by them. For examples of illicit process, see the subfallacies.


Irving Copi & Carl Cohen, Introduction to Logic (Tenth Edition) (Prentice Hall, 1998), pp. 276-7.