More fun with squids, giraffes, and proper reasoning.

[Angra Mainyu]

Let us consider the following two scenarios.

S1: Let us suppose that Bob and Alice live in an isolated rural community, and have never heard of giraffes, moluscs, squids, elephants, or any of those things. But they meet Daniel, who is not from their community. In the context of their conversations, they have the following exchange (in which both Alice and Bob are being sincere).

Daniel: A giraffe is not a mollusc.
Daniel: Tom is either a squid or a giraffe.
Daniel: Tom is a mollusc.
Alice: I get it. Tom is a squid.
Bob: You don't know that.
Alice: Well, I'm saying that on the basis of what Daniel said, Tom is a squid. I do not know whether Daniel is mistaken or pulling our legs - no offense, Daniel -, but on the basis of what he said, Tom is a squid.
Bob: No, you shouldn't make that assessment on the basis of the information given by Daniel.
Alice: You are not reasoning properly, Bob.

S2: Let us suppose that Bob and Alice live in an isolated rural community, and have never heard of giraffes, moluscs, squids, elephants, or any of those things. But they meet Daniel, who is not from their community. In the context of their conversations, they have the following exchange (in which both Alice and Bob are being sincere).

Daniel: A giraffe is not a elephant.
Daniel: Tom is either a squid or a giraffe.
Daniel: Tom is an elephant.
Alice: I get it. Tom is a squid.
Bob: You don't know that.
Alice: Well, I'm saying that on the basis of what Daniel said, Tom is a squid. I do not know whether Daniel is mistaken or pulling our legs - no offense, Daniel -, but on the basis of what he said, Tom is a squid.
Bob: No, you shouldn't make that assessment on the basis of the information given by Daniel.
Alice: You are not reasoning properly, Bob.

So, who is reasoning properly in these scenarios? Alice or Bob? Or neither? Or is it one on each scenario? What do you think?

 

[bilby]

Bob is correct in both cases. 'X is not a Y' doesn't imply 'Y is not an X'.

Not all hot tubs are jacuzzis, but all jacuzzis are hot tubs. All thumbs are fingers, but not all fingers are thumbs. Even Zach on BBT got that right.

As Alice and Bob know nothing of giraffes, molluscs, squids or elephants, they are not able to determine which of those things are (or might be) subsets of others.

 

[Angra Mainyu]

Bob is correct in both cases. 'X is not a Y' doesn't imply 'Y is not an X'.

Not all hot tubs are jacuzzis, but all jacuzzis are hot tubs. All thumbs are fingers, but not all fingers are thumbs. Even Zach on BBT got that right.

As Alice and Bob know nothing of giraffes, molluscs, squids or elephants, they are not able to determine which of those things are (or might be) subsets of others.

Alice is right in both cases, and Bob mistaken in both, but I guess you interpret "A giraffe is not a mollusc" differently. What do you think that that means?
It's interesting, because perhaps that would explain the results in the other thread, rather than systematic logic mistakes.

 

[bilby]

Bob is correct in both cases. 'X is not a Y' doesn't imply 'Y is not an X'.

Not all hot tubs are jacuzzis, but all jacuzzis are hot tubs. All thumbs are fingers, but not all fingers are thumbs. Even Zach on BBT got that right.

As Alice and Bob know nothing of giraffes, molluscs, squids or elephants, they are not able to determine which of those things are (or might be) subsets of others.

Alice is right in both cases, and Bob mistaken in both, but I guess you interpret "A giraffe is not a mollusc" differently. What do you think that that means?
It's interesting, because perhaps that would explain the results in the other thread, rather than systematic logic mistakes.

I thought I already explained it. 'A giraffe is not a mollusc' doesn't imply 'a mollusc is not a giraffe'.

A car is not a blue 2014 Toyota Camry. But a blue 2014 Toyota Camry is a car.

Hierarchies exist; In the absence of knowledge about what words refer to what hierarchical levels, and which entities are proper susets of which other entities, it's not correct to assume that identity relationships are commutative.

 

[Angra Mainyu]

I thought I already explained it. 'A giraffe is not a mollusc' doesn't imply 'a mollusc is not a giraffe'.

A car is not a blue 2014 Toyota Camry. But a blue 2014 Toyota Camry is a car.

That clearly indicates that you do not interpret "A car is not a blue 2014 Toyota Camry" to mean something equivalent to "For all X, if X is a car, then X is not a blue Toyota Camry". So, there is a clear difference in interpretation of the premise. I wonder whether that would at least partially explain Speakpigeon's results in other threads.

 

[bilby]

I thought I already explained it. 'A giraffe is not a mollusc' doesn't imply 'a mollusc is not a giraffe'.

A car is not a blue 2014 Toyota Camry. But a blue 2014 Toyota Camry is a car.

That clearly indicates that you do not interpret "A car is not a blue 2014 Toyota Camry" to mean something equivalent to "For all X, if X is a car, then X is not a blue Toyota Camry". So, there is a clear difference in interpretation of the premise. I wonder whether that would at least partially explain Speakpigeon's results in other threads.

Maybe.

English is a dreadful language for expressing anything precise. That's why mathematicians use algebra instead.

 

[fast]

The first premise was killing me. That “not” was throwing me for a loop. So, I sounded it out like a kid and after several rounds of wtf, this is what I did: I rearranged the order:

Tom is either a squid or a giraffe. That’s it, one or the other. Squid or a giraffe. Squid or a giraffe. All I needed to do was keep saying that and hoping for a sign. Did I get one? Yes.

Tom is a mollusc. Oh great, like that helps. It’s something! But gee, that’s not enough. If only I knew how that fitted in! Right now, all I have to go on is what’s commited to eternal memory (squid or giraffe) and now that he’s definitely a mollusc.

Next, the wretched first premise rears it’s ugly twisted head with that fiendishly dreaded “not” paving the way for thinking something ain’t right.

A giraffe is not a mollusc. Wait, what? Who gives a shit? How does that help? So, back to the drawing board.

What do I know? Squid or giraffe and is a mollusc and a giraffe is not a mollusc. Wait. Let me mentally write, (not a mollusc) with giraffe and get this:

Tom is a squid or giraffe (not a mollusc). Now I’m associating giraffe and not a mollusc. Holy smokes, a giraffe is not a mollusc and Tom is a mollusc.

Tom is a squid!!

 

[Angra Mainyu]

The first premise was killing me. That “not” was throwing me for a loop. So, I sounded it out like a kid and after several rounds of wtf, this is what I did: I rearranged the order:

Tom is either a squid or a giraffe. That’s it, one or the other. Squid or a giraffe. Squid or a giraffe. All I needed to do was keep saying that and hoping for a sign. Did I get one? Yes.

Tom is a mollusc. Oh great, like that helps. It’s something! But gee, that’s not enough. If only I knew how that fitted in! Right now, all I have to go on is what’s commited to eternal memory (squid or giraffe) and now that he’s definitely a mollusk.

Next, the wretched first premise rears it’s ugly twisted head with that fiendishly dreaded “not” paving the way for thinking something ain’t right.

A giraffe is not a mollusc. Wait, what? Who gives a shit? How does that help? So, back to the drawing board.

What do I know? Squid or giraffe and is a mollusc and a giraffe is not a mollusc. Wait. Let me wrote (not a mollusc with giraffe and get this:

Tom is a squid or giraffe (not a mollusc). Now I’m associating giraffe and not a mollusc. Holy smokes, a giraffe is not a mollusc and Tom is a mollusc.

Tom is a squid!!

Indeed, he is a squid!

 

[A Toy Windmill]

To help Bilby, rephrase premise 1 as:

1) No giraffe is a mollusc.

 

[bilby]

To help Bilby, rephrase premise 1 as:

1) No giraffe is a mollusc.

That's a distinct improvement in clarity.