Something maybe one of you guys might be interested in...

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Something maybe one of you guys might be interested in...

Post  HSW on Sun Jan 23, 2011 5:34 pm

Just doing a quick independent study-type (Sorry to use that horrific phrase and bring up terrible memories guys) peice of work for my philosophy module - The Art Of Persuasion. (Yes, it's Critical Thinking, back to haunt us all - wish me some serious amounts of luck).

Thought I'd share one of the things we have been told to do - maybe you'll find it interesting, here goes:

Four of the following involve logical errors and two are valid (thought they may not be sound!).

(The question being asked - Basically, they may not make any sense at all, but if all the claims were 100% truth, is the conclusion drawn from those statements alone, correct?)

A) See if you can tell which are invalid and which are valid.
B) See if you can identify where the invalidity of each false argument lies.


1. The Illustrated History of Witches is a book.
Some books have pictures.
Therefore, The Illustrated History of Witches has pictures.

My Guess: Invalid

2. If the town is French then it is haunted by ghosts.
Stoke-on-Trent is not a town in France.
Therefore, Stoke-on-Trent is not haunted by ghosts.

My Guess: Invalid

3. Only witches’ cats do not fall off broomsticks in flight
My cat does not fall off a broomstick in flight
My cat belongs to a witch

My Guess: Valid

4. If something is a werewolf, then it is brown.
Fido is brown.
Therefore, Fido is a werewolf.

My Guess: Invalid

5. If it is Halloween, the spirits will be abroad.
The spirits are not abroad.
It is not Halloween.

My Guess: Valid

6. It is false that if something is a ghost, then it is evil.
Therefore, if it is a ghost, then it is not evil.

My Guess: Invalid

I will edit this post to include the correct answers when I find them out. If you want the reasoning behind my guess, give me a shout.

Hope it's at least vaguely interesting to you guys - I found it to be an alright exercise. Almost like some sort of brain teaser.

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Re: Something maybe one of you guys might be interested in...

Post  HyPeR-09 on Sun Jan 23, 2011 7:50 pm

This is just like the shit I do in maths, but with algebra and relations.

I agree with all your answers apart from the last two.

HSW wrote:5. If it is Halloween, the spirits will be abroad.
The spirits are not abroad.
It is not Halloween.

My Guess: Valid

6. It is false that if something is a ghost, then it is evil.
Therefore, if it is a ghost, then it is not evil.

My Guess: Invalid

5)

IF it is Halloween, the spirits will be abroad.
So Halloween implies abroad. Being abroad doesn't imply Halloween.
Had the rule said if and only if it is Halloween, the spirits will be abroad then the statement implies both ways.

My Guess: 5 is invalid.

EDIT: Shit. I keep reading things wrong. I do agree with you. They have to be abroad for it to be Halloween and they ain't abroad. It's not Halloween

I think I read They are abroad, therefore it is Halloween.
6)

After re-reading I agree with you on 6. Just because less than 100% are evil doesn't mean no ghosts are evil.
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Re: Something maybe one of you guys might be interested in...

Post  HSW on Sun Jan 23, 2011 8:11 pm

Hehehe. Yeah you're tracking and backtracking along all the similar lines that I did when I read it and re-read it all - good to see. The last one was mostly down to deduction through the given information in the question - only two are valid. Obviously, by the last question, I'd already found what I considered to be the two valid ones.

EDIT: Ah yeah of course. Your explanation for the last one being valid makes sense. I knew there was something there that I was overlooking. I was kinda cycling through: (Ghost = Evil) is not true. Which does not mean Ghost = Not evil. But for some reason I overlooked the quantity of ghosts that are evil. Nice.

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Re: Something maybe one of you guys might be interested in...

Post  aPhRo_ on Sun Jan 23, 2011 9:56 pm




1. if you take the fact it is illustrated as one of the facts. then surely point 1 is valid? however if you see it form a purely logical side:

1. is invalid,
2. is invalid
3. is valid
4. is valid, under the logic of what you've been told
5. is valid
6. is invalid



"This bridge is sound, sounds are vibrations in the air,
Therefore this bridge is a vibration in the air."
logically valid or not?
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Re: Something maybe one of you guys might be interested in...

Post  HSW on Mon Jan 24, 2011 9:23 am

aPhRo_ wrote:"This bridge is sound, sounds are vibrations in the air,
Therefore this bridge is a vibration in the air."
logically valid or not?

This, I think, would be a valid argument. Valid only means that it makes logical sense if everything you are told is true.

That is, if by "This bridge is sound" you mean that the bridge is noise. If you mean to use a different definition of sound, the other in my mind being "secure/safe/solid" (Mr Dillon-esque) then it doesn't make sense, obviously.

Going back to this:

4. If something is a werewolf, then it is brown.
Fido is brown.
Therefore, Fido is a werewolf.

The way I see it (because we didn't go over these answers today):

Werewolves are brown. This does not mean that everything brown is a werewolf.
So - Fido being brown does not guarantee mean that fido is a werewolf.

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Re: Something maybe one of you guys might be interested in...

Post  HyPeR-09 on Mon Jan 24, 2011 11:39 am

aPhRo_ wrote:"This bridge is sound, sounds are vibrations in the air,
Therefore this bridge is a vibration in the air."
logically valid or not?

You used the grammar to mean that the bridge is sound, not a sound.
Therefore, the bridge is not definitely a sound.
You cannot conclude the bridge is a vibration in the air.

It's initially unclear - but if the grammar is correct in the way you typed it then the argument is invalid.

HSW wrote:The way I see it (because we didn't go over these answers today):

Werewolves are brown. This does not mean that everything brown is a werewolf.
So - Fido being brown does not guarantee mean that fido is a werewolf.

Use the same logic I used when I misread 5).

1) Being a werewolf means you are definitely brown.
2)It does not define that the only brown things are werewolves. Thus the fact that Fido is brown doesn't mean shit.

You can't conclude Fido is a werewolf.

Spoiler:
He could just be indian...
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Re: Something maybe one of you guys might be interested in...

Post  Randle on Mon Jan 24, 2011 12:06 pm

Haha, when I was skim reading over the comments I thought I saw Chris H say "Tracking and backsmacking" Razz


1. Invalid

2. Invalid

3. Invalid

4.Invalid

5. Valid

6. Valid

Man these have the same feel as Catholics trying to make a good argument. Very Happy "Perfection exists, God is perfect, therefore God exists."

"This bridge is sound, sounds are vibrations in the air,
Therefore this bridge is a vibration in the air."
logically valid or not?

I agree with Chris J on this one:

HyPeR-09 wrote:
You used the grammar to mean that the bridge is sound, not a sound.
Therefore, the bridge is not definitely a sound.
You cannot conclude the bridge is a vibration in the air.

It's initially unclear - but if the grammar is correct in the way you typed it then the argument is invalid.

Haha nice Chris, just found out what that white bar was Razz

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Re: Something maybe one of you guys might be interested in...

Post  HSW on Mon Jan 24, 2011 3:37 pm

Ah right yeah no erm. I was just rolling with it as if it was a noise. I guess you cant really say that *something* is sound, and mean noise? Or can you?

"Music is sound that is enjoyable to listen to." (e.g)

I think maybe you can. Anyway, yeah, you guys get my original point. Hopefully sam gets it too Razz.

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Re: Something maybe one of you guys might be interested in...

Post  HyPeR-09 on Mon Jan 24, 2011 4:15 pm

HSW wrote:Ah right yeah no erm. I was just rolling with it as if it was a noise. I guess you cant really say that *something* is sound, and mean noise? Or can you?

"Music is sound that is enjoyable to listen to." (e.g)

I think maybe you can. Anyway, yeah, you guys get my original point. Hopefully sam gets it too Razz.

I hadn't thought about it like that... but I guess here music is plural and thus different.

If singular, e.g. "A piece of music is sound that is enjoyable to listen to.", I don't think that makes sense. At least, it doesn't read correctly grammatically. There are ways you could make it flow better.
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Re: Something maybe one of you guys might be interested in...

Post  HSW on Mon Jan 24, 2011 4:37 pm

Yeah agreed - you can make it flow better.

But this is all irrelevant to what we were talking about anyway (in the sense that it's grammar affecting the logic, not just the logic itself). So yeah. We are mostly in agreement. Sweet.


study

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Re: Something maybe one of you guys might be interested in...

Post  aPhRo_ on Tue Jan 25, 2011 3:35 am

Looking at it again and looking at it completely logically, we did logic in the very first week in my maths class and it can be applied here:

For something to be valid: the logical structure of an argument is ok, but premises may not be.

If something is a werewolf, then it is brown.
Fido is brown.
Therefore, Fido is a werewolf.

if A == B
D == B

D == A

Logically you can't imply that D is = to A therefore the argument is invalid. Very Happy

The sound one
For something to be valid: the logical structure of an argument is ok, but premises may not be.

therefore it is a valid argument, but not a "sound" argument.
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Re: Something maybe one of you guys might be interested in...

Post  HyPeR-09 on Tue Jan 25, 2011 10:55 am

aPhRo_ wrote:Looking at it again and looking at it completely logically, we did logic in the very first week in my maths class and it can be applied here:

For something to be valid: the logical structure of an argument is ok, but premises may not be.

If something is a werewolf, then it is brown.
Fido is brown.
Therefore, Fido is a werewolf.

if A == B
D == B

D == A

Logically you can't imply that D is = to A therefore the argument is invalid. Very Happy

The sound one
For something to be valid: the logical structure of an argument is ok, but premises may not be.

therefore it is a valid argument, but not a "sound" argument.

In that case, you meant that a bridge is A sound, not that the bridge IS sound. This is what we were disputing. Grammatically, it makes it unclear. If you were calling is A sound... You said:

Bridge is A sound -> Sounds are waves -> Bridge is a sound and is therefore vibrations.

If you had typed this, I would've said the argument was valid.
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