What makes a syllogism commit the fallacy of illicit major or illicit minor?

In logic, the fallacies of illicit major and illicit minor are formal fallacies that occur when a syllogism violates the rules of distribution.

A term is considered distributed when a statement refers to all members of the class that the term denotes. The fundamental principle of formal inference in a categorical syllogism is that no term may be distributed in the conclusion unless it was also distributed in the premise where it appeared.12

• Illicit Major: This occurs when the major term (the predicate of the conclusion) is distributed in the conclusion but was not distributed in the major premise.13
• Illicit Minor: This occurs when the minor term (the subject of the conclusion) is distributed in the conclusion but was not distributed in the minor premise.13

Essentially, these fallacies arise because the argument attempts to make a universal claim about a class in the conclusion that the premises did not fully support.12