Undistributed middle

The Undistributed middle is a fallacy similar to to Equivocation, except that 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.

Examples

 * Example 1
 * All cats use air.
 * All gasoline engines use air.
 * Therefore, all cats are gasoline engines.


 * Example 2
 * Science uses the word Theory.
 * Creationism uses the word Theory.
 * Thus, Creationism is science.


 * Example 3
 * All fish live in water.
 * All whales live in water.
 * Therefore, all whales are fish (They're not - they're mammals)