Logical Fallacies
Logical Fallacies / Syllogistic Fallacies

Syllogistic Fallacies

When logical fallacies occur in the syllogisms of deductive reasoning. This occurs with a reference to something general, and then makes a conclusion about something more specific.

Definition of a categorical syllogism is an argument with two premises: one syllogism and one conclusion.

  • A: All S are P. (Ex. All dogs are mammals.)
  • E: No S are P. (Ex. No cats are fish.)
  • I: Some S are P. (Some logicians are philosophers.)
  • O: Some S are not P. (Some men are not clowns.)

Example of Syllogistic Fallacies

  • All sharks are fish (All S are P.) All salmon are fish (All x are P). Therefore all salmon are sharks. (All x are P.)The two generalities in the first two statements are true, but they do not validate the conclusion being drawn.
  • No philosophers are elephants.All elephants are mammals.Therefore no philosophers are mammals.Though it is true that there are no philosophers that are elephants, and that all elephants are in fact mammals. These do not negate the fact that philosophers (humans) are mammals.


Alternative Name: Fallacy of the Undistributed Middle