Name This Fallacy

Factual Questions
1
  1. Bob argues that Event A has occurred to Sue
  2. Bob says that as proof of Event A, Sue will perform Activity B
  3. Activity B would be expected if Event A occurred or did not occur
  4. Sue performs Activity B, Bob claims this proves Event A has occurred

Is there a name for this flaw in logic? I can’t seem to find similar examples on Wikipedia etc.

2

It’s a variation on affirming the consequent.

3

Post hoc ergo propter hoc? (After this therefore because of this).

4

I generally don’t see the point in concerning oneself with specific names for fallacies. Whoever it is you want to point out the fallaciousness of this argument form to, just direct their attention to step 3: Activity B occurs whether or not Event A occurs. That is, Activity B has absolutely no given logical connection with Event A; the two have nothing to do with each other. So, of course, it would be wrong to think the performing of Activity B somehow proves Event A occurred.

5

Lost the edit window, but I wanted to end that post with:

Bringing out a name and linking them to a page on “The Fallacy of the Morchivicated Exponential” is only going to impart less understanding of the problem than an actual explanation like this, not more.

6

Thanks everyone, your responses have been most helpful. And Indistinguishable, I would generally agree, but this person tends to not follow basic logic that well. The plan is to point out the flaw in step 3 and say ‘look, there’s even a name for this type of fallacy, other people make the same mistake’. I know, I know…not very logical :slight_smile:

7

Now, sir, you are well aware that the Fallacy of the Morchivicated Exponential is not readily accepted as applicable outside of the realm of derivated brachiophiling. Please stop misleading the masses with this sort of talk. :mad:

8

I agree:

If A, then B.
B.
Therefore, A.

Affirming the consequent, a.k.a. the Fallacy of the Converse.

(Just because an implication, like A --> B, is true, doesn’t mean its converse B --> A is necessarily true.)

9

When a debater is blatant and arrogant in his use of a logical fallacy, it has its own category. It is called Fallacio, because it sucks.