When we reason about groups and categories, the pieces have to fit together snugly, like a jigsaw puzzle. The first thing that fits might be misleading.
A categorical syllogism where the middle term is not distributed in at least one premise.
The major term is distributed in the conclusion but not distributed in the major premise.
The minor term is distributed in the conclusion but not distributed in the minor premise.
A categorical syllogism that appears to have three terms but actually has four due to equivocation.