Structural Fallacies

Structural fallacies are great. You know that when someone's argument is structurally false, their argument is wrong, despite the content of their argument. The way they argued their point makes them automatically wrong. Most of these types of fallacies are arguing backwards. An example of this type of structural fallacy would be this:

(All) fat people are jolly.

I'm jolly.

Therefore, I'm fat.

Assuming all fat people are jolly, (which isn't true), the fact that I'm also jolly does not necessarily mean that I'm fat. While I could be fat, being jolly does not make me fat. That is backwards reasoning. To put it more simply, the backwards argument goes like this:

All A is B.

C is B.

Because all A is B and C is also B, C is A.

So when someone's argument is structured in this way, you know that despite the content, the argument is very weak because its structure is unrepairable. So even if you agree with someone's content, you should still point out that their argument is weak because of their weak structure.