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  #1  
Old Thursday, November 29, 2012
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Default A query about categorical syllogism
Dear all
AOA
I am bit confused about a particular problem of form and validity in categorical syllogism, please go through it and suggest where i am mistaken

consider these categorical syllogism of form AAA-3

all terriers are dogs
all terriers are mammals
therefore, all mammals are dogs

the second one is

all terriers are mammals
all terriers are dogs
therefore all dogs are mammals

both these are in standard form, having true premises and same form but former has false conclusion and so is invalid and later has true and so is a valid argument.

please justify it??

regards
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  #2  
Old Friday, December 14, 2012
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the 2nd is also an invalid argument.
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  #3  
Old Sunday, December 30, 2012
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Dear hassan,
many thanks for your reply
can you answer how is it an invalid argument as its conclusion is logically derived from its premises and is true as well.
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Old Thursday, February 21, 2013
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@abdulmoqeet

Well, logically speaking AAA-3 form commits the fallacy of Illicit Minor, i.e. its minor term(dogs) is distributed in the conclusion but not in minor premise(all terriers are dogs).

If an argument is valid and its premises are true, its conclusion cannot be false. Its converse statement: In a valid argument, the conclusion is logically warranted by the premises. But an invalid argument can have both true premises and true conclusion, as the case is of your 2nd argument. Validity does not mean that argument must have true premises and true conclusion, it requires the argument to conclusively claim that its conclusion is entailed in its premises. The logic tests that claim, and six tests are usually used as were developed by logicians. Your argument fails the third test.
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Old Tuesday, December 24, 2013
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If the first premise is False
The 2nd premise is also False
and these premises are forcing the conclusion to be False

Then this too would be called a valid argument. Regardless of the fact that both premises are true.
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Old Monday, December 30, 2013
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Quote:
Originally Posted by Haris89 View Post
If the first premise is False
The 2nd premise is also False
and these premises are forcing the conclusion to be False

Then this too would be called a valid argument. Regardless of the fact that both premises are true.
Brother what you have said is just incorrect, Validity is the formal characteristic of deductive arguments, an argument is valid only if the truth of its premises entails the truth of its conclusion. So my friend its the TRUTh of the premises not the falsity that forces the conclusion to be true.

Regards,
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Old Monday, December 30, 2013
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Quote:
Originally Posted by Haris89 View Post
If the first premise is False
The 2nd premise is also False
and these premises are forcing the conclusion to be False

Then this too would be called a valid argument. Regardless of the fact that both premises are true.
Validity doesn't have anything to do with the truth of the statements. The false premises don't force the conclusion to be false, they are independent statements and have their own truth value. Yes all three statements could be false and it would still be a valid argument.
Example:
All women are astronauts.
Socrates is a woman.
Therefore, Socrates is an astronaut.
The argument is valid but unsound.
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Old Monday, December 30, 2013
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Quote:
Originally Posted by Bilal Hassan View Post
Brother what you have said is just incorrect, Validity is the formal characteristic of deductive arguments, an argument is valid only if the truth of its premises entails the truth of its conclusion. So my friend its the TRUTh of the premises not the falsity that forces the conclusion to be true.

Regards,
What my brother above is talking about is what i am saying also. True and false premise has nothing to do with the Argument being a valid one.

REGARDS
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  #9  
Old Monday, December 30, 2013
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Originally Posted by Buddha View Post
Validity doesn't have anything to do with the truth of the statements. The false premises don't force the conclusion to be false, they are independent statements and have their own truth value. Yes all three statements could be false and it would still be a valid argument.
Example:
All women are astronauts.
Socrates is a woman.
Therefore, Socrates is an astronaut.
The argument is valid but unsound.
Indeed, the false premises don't necessarily entail a false conclusion, it is about that incontrovertible proof they give for the deduction of conclusion. If an argument have true premises which also deduce a true conclusion as well as conclusion logically follows from the premises then it is a sound argument, but if premises are false but conclusion logically follows from premises then it is still valid but not sound. Thanks for the input.
Quote:
Originally Posted by Haris89 View Post
What my brother above is talking about is what i am saying also. True and false premise has nothing to do with the Argument being a valid one.

REGARDS
Yes dear but you must also appreciate the deductive arguments in terms of being sound and unsound, validity is just one formal aspect of arguments, and in your earlier post you were talking about false premises entailing a false conclusion, its not always the case that false premises lead to false conclusion, if an argument has false premises and still has a true conclusion but it follows logically from premises then still its a valid argument.
Example:
All mammals have wings.
All birds are mammals.
Therefore, All birds have wings.

So you got my point, an argument is still valid if it has false premises and true conclusion, as my example suggests. Separate statements have separate truth values, you must see the inner structure of arguments to find whether they are valid or not.

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  #10  
Old Tuesday, December 31, 2013
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Yes bilal my area of concern was the validity of the Argument and not its soundness , as you can see in my original post.

Regards
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