Undistributed Middle
The undistributed middle fallacy reasons that because two groups share a property they are the same group, for example "all cats are mammals, all dogs are mammals, so cats are dogs". Debaters answer by showing that sharing a property does not link the groups.
Undistributed Middle as it appears in championship debate rounds. Each example below is a moment from a real round, with a note on why it illustrates the technique and how a debater can use it, or answer it.
Example 1
The 1AR calls out the negative's liberalism link as a 'pants' argument: 'you're liberal and Iraq was liberal, so therefore you're Iraq.' This is an undistributed middle. Sharing one trait (liberalism) with a bad thing does not make two things the same, especially when liberalism has many aspects, like respect for human life. When an opponent's link rests only on a shared label, name the missing middle term and demand they show why this specific version of the trait causes the harm.
Sources: every example links to the YouTube video of the championship debate it comes from, at the moment described.
All techniques and fallacies