The Undistributed middle is a similar fallacy to Equivocation, except, instead of conflating definitions, two different things are equated due to a common middle ground that is misused. The argument is assuming that the set of Object-A that has the middle ground intersects with the set of Object-B that has the same middle ground.
Here are some examples of the undistributed middle:
- Example 1
- All cats use air.
- All gasoline engines use air.
- Therefore, all cats are gasoline engines.
- Example 2
- Example 3
- All fish swim in the ocean.
- All whales swim in the ocean.
- Therefore, all whales are fish (They're not - they're mammals)