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All X are Y, but not all Y are X- Critical thinking- what is the term for this?
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Ron Potter
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Forum User
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'All X are Y, therefore All Y are X' is a logical fallacy, though again I don't know that it has a particular name. Perhaps 'converse fallacy'?
What does this have to do with law?
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Mill Hill
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Ron Potter
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#4
(Original post by Mill Hill)
All dogs are mammals, but not all mammals are dogs, for example.
All dogs are mammals, but not all mammals are dogs, for example.
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Ron Potter
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#5
(Original post by Forum User)
'All Y are X' is the converse of the statement 'all X are Y'. If a statement is true then its converse might be true, or it might not. As far as I know, there isn't a special term for a statement's converse not being true.
'All X are Y, therefore All Y are X' is a logical fallacy, though again I don't know that it has a particular name. Perhaps 'converse fallacy'?
What does this have to do with law?
'All Y are X' is the converse of the statement 'all X are Y'. If a statement is true then its converse might be true, or it might not. As far as I know, there isn't a special term for a statement's converse not being true.
'All X are Y, therefore All Y are X' is a logical fallacy, though again I don't know that it has a particular name. Perhaps 'converse fallacy'?
What does this have to do with law?
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UWS
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Notoriety
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#7
It's valid if it's true. You're not concluding anything from it, so I don't suppose it could attract the label of a logical fallacy. Once you actually do something with it, it might become a syllogism or one of the fallacies posted in this thread.
As above, I don't see how this pertains to law.
As above, I don't see how this pertains to law.
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Ron Potter
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what form/fallacy is this? for example (the one that is confusing me)
An animal is not a dog unless it is brown. But it does not follow that if an animal is brown it is a dog
An animal is not a dog unless it is brown. But it does not follow that if an animal is brown it is a dog
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MagneticNorth
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Shibu the Doge
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#10
X = 9
Y= revise
All the students that get a 9, revise, but not all the students who revise get a 9
Y= revise
All the students that get a 9, revise, but not all the students who revise get a 9
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Ron Potter
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username3911170
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#12
(Original post by Ron Potter)
how do i remove then?
how do i remove then?
with love,
Mrs.Hermione Malvoy (ew..)
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Ron Potter
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#13
(Original post by Çharmander)
it’s not possible mr.potter, unless u ask the mods to do so.
with love,
Mrs.Draco Granger
it’s not possible mr.potter, unless u ask the mods to do so.
with love,
Mrs.Draco Granger
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username3911170
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#14
(Original post by Ron Potter)
How?
How?
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gjd800
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#15
Well, if then conditionals are not symmetrical, so if
P is 'animal is a dog' and Q is 'animal barks', then we have
P → Q
If animal is a dog, then the animal barks. This is true, and allows no counterexample. Everything that is a dog barks.
Then take
Q → P
If animal barks then it is a dog. This is false, because we have at least one counterexample - seals bark and they are not dogs.
So
(P → Q) ~≡ (Q → P)
If P then Q is not equivalent to if Q then P.
Thus it does not follow from 'if an animal is a dog, it barks' that 'if an animal barks, it is a dog'.
P is 'animal is a dog' and Q is 'animal barks', then we have
P → Q
If animal is a dog, then the animal barks. This is true, and allows no counterexample. Everything that is a dog barks.
Then take
Q → P
If animal barks then it is a dog. This is false, because we have at least one counterexample - seals bark and they are not dogs.
So
(P → Q) ~≡ (Q → P)
If P then Q is not equivalent to if Q then P.
Thus it does not follow from 'if an animal is a dog, it barks' that 'if an animal barks, it is a dog'.
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carrotstar
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#16
(Original post by Ron Potter)
what form/fallacy is this? for example (the one that is confusing me)
An animal is not a dog unless it is brown. But it does not follow that if an animal is brown it is a dog
what form/fallacy is this? for example (the one that is confusing me)
An animal is not a dog unless it is brown. But it does not follow that if an animal is brown it is a dog
Try to think of alternative ways of saying the same thing.
For example, all reds are a colour, but not all colours are red.
All parsnips are vegetables, but not all vegetables are parsnips.
All paper is flat, but not all flat things are paper.
You can apply this rule to most things which sit in a category alongside other items.
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gjd800
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#17
As I said in your other thread...
Well, if then conditionals are not symmetrical, so if
P is 'animal is a dog' and Q is 'animal barks', then we have
P → Q
If animal is a dog, then the animal barks. This is true, and allows no counterexample. Everything that is a dog barks.
Then take
Q → P
If animal barks then it is a dog. This is false, because we have at least one counterexample - seals bark and they are not dogs.
So
(P → Q) ~≡ (Q → P)
If P then Q is not equivalent to if Q then P.
Thus it does not follow from 'if an animal is a dog, it barks' that 'if an animal barks, it is a dog'.
If you were to say that
(1) If an animal barks, it is a dog
(2) A seal barks
(C) A seal is a dog
You would be affirming the consequent, which UWS pointed out in your other thread.
Well, if then conditionals are not symmetrical, so if
P is 'animal is a dog' and Q is 'animal barks', then we have
P → Q
If animal is a dog, then the animal barks. This is true, and allows no counterexample. Everything that is a dog barks.
Then take
Q → P
If animal barks then it is a dog. This is false, because we have at least one counterexample - seals bark and they are not dogs.
So
(P → Q) ~≡ (Q → P)
If P then Q is not equivalent to if Q then P.
Thus it does not follow from 'if an animal is a dog, it barks' that 'if an animal barks, it is a dog'.
If you were to say that
(1) If an animal barks, it is a dog
(2) A seal barks
(C) A seal is a dog
You would be affirming the consequent, which UWS pointed out in your other thread.
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#18
(Original post by Ron Potter)
its something i cam across and i just don't understand. its example was: A animal is not a dog unless it barks. but it does not follow that if an animal barks it is a dog.
its something i cam across and i just don't understand. its example was: A animal is not a dog unless it barks. but it does not follow that if an animal barks it is a dog.
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#19
Why is q the premise in that argument? I never did any formal logic but it seems that the two premises are 'p implies q' and 'p', and that q is the conclusion?
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the bear
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#20
all Premier Division footie people identify as male
not all people who identify as male are Premier Division footie people
not all people who identify as male are Premier Division footie people
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