Syllogistic

Syllogistic fallacies are kinds of invalid categorical syllogisms. This list contains the fallacy of undistributed middle and the fallacy of four terms, and a few others though there are a great many such formal fallacies.

Logical

See Formal.

Formal

Formal fallacies are all the cases or kinds of reasoning that fail to be deductively valid. Formal fallacies are also called logical fallacies or invalidities.

Example:

Some cats are tigers. Some tigers are animals. So, some cats are animals.

This might at first seem to be a good argument, but actually it is fallacious because it has the same logical form as the following more obviously invalid argument:

Some women are Americans. Some Americans are men. So, some women are men.

Nearly all the infinity of types of invalid inferences have no specific fallacy names.