Which logical fallacy is this?

I cannot remember the name of this logical fallacy: “I am tall; giraffes are tall; therefore; I am a giraffe.”

It’s a hasty generalisation.

A hasty generalisation comes from a situation where you don’t have enough data to form a conclusion. If a child were told that a giraffe is a tall animal and concluded that you were a giraffe then that would be a hasty generalisation.

Affirming the consequent

Looks like Undistributed middle.

It is not affirming the consequent, since there is no conditional in the argument. I agree with John Mace, Undistributed Middle seems the best fit.

I’ll second Eleusis. From that link:

And now I’ll retreat to the undistributed middle term being “tall.”

[sub]You don’t know me. You can’t tell my boss what I said first.[/sub]

If giraffe, then tall.
Therefore, giraffe.

The OP is a logical fallacy. “Undistributed middle” is a logical fallacy.

Therefore the OP is “undistributed middle”.


I get it. Hegel will get it.

Therefore hegel is Eleusis.

No wait.

John Mace just confirmed my point for those confused.
One more time:

If Eleusis, then get it.
Get it.
Therefore, Eleusis.

Get it?

Is there an essential difference between the two fallacies?

Are there statements that can be written in one form that cannot be written in the other?

AC = UM?

Unable to construe differences, I hereby concede that “Undistributed Middle” is an equally valid logical fallacy in the “I am a giraffe” conspiracy.

The undistributed middle fallacy applies when a common feature of two seperate groups is used to argue they are alike in every respect. The affirmation of the consequent, however, only applies when a conclusion is used to prove its premise. It’s a fallacy because there can potentially be other premises/causes… hang on - those two are exactly the same.

So it’s my reckoning that the OP does demonstrate an undistributed middle fallacy, but only because of how it’s phrased. They (the fallacies) seem to be pretty much identical, the only apparent difference being that the AOC must contain a conditional statement, and UM a declarative.

Anybody out there who’s done more than 6 months of coursework on logic?

I am Eleusis and so’s my wife!

Sadlly, that would be me. But it was so long ago, it might as well never have happened.

They sure do seem equivalent to me, although the OP is worded in the form of an undistributed middle. But since they are both fallacies, might it be impossible to prove that they are equivalent?

JOAN OF ARGGHH! and **Friedo[/] would probably say fecetious. :smiley:

A little more. Part of the problem is that it depends on how one translates the sentences into logical terms. There are two basic kinds of symbolic logic (I realize that this is a vast oversimplification, and quite possibly utter twaddle):

Propositional logic

If A, then B
A is the case.
Therefore B is the case.

and Quantification theory logic

All men are mortal
Socrates is a man
Therefore Socrates is mortal

In the first case, we are not ascribing any qualities to the terms, in the second that is what it is all about. It is a form of modal logic that talks about quantities. All, some, and none.

We could write the OP fallacy like this, in propositional logic:

Since we are talking about categories and attributes, we are in the modal/quantification realm, and affirming the consequent just doesn’t fit the structure. Affirming the consequent is an error of propositional logic.

One could try to cram it into the AC model like this:

A=a thing is a giraffe
B=a thing is tall

And then it would look like this:

If A, then B. B. Therefore A.

But we are talking about a specific instance of B (I am tall) versus a universal statement about B ((all) giraffes are tall). The nuance is lost by this formulation.

Here are some fun references




I was looking at it like this:

Giraffes are a subset of things that are tall.
I am a subset of things that are tall.
Therefore, the subset “giraffes” and the subset “I” are equivalent.

That can be writtin symbolically (although I don’t know how to do so in this text editor). So, can it be shown to be mathematiaclly equivalent to the symbolic representation of affirming the consequent?

Not really. Subsets, in the sense you are using the term, are part of the logic of some, all, and none. You are really saying, all giraffes have property t. (You might express this G(t)); I have property t (I(t)), Therefore, I is materially equivalent to G. These are statements about properties of I and G, even as you expressed them. There may be some way to do it, and here is a page to get you started in the translation. Translation into symbolic logic

I guess my question is why would you want to?

The last sentence in what you quoted from me is why.

To show, mathematically, that AC = UM (or not).