A OR D??!!

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mehaksal: Master | Next Rank: 500 Posts; Posts: 122; Joined: Tue Jul 10, 2012 9:12 am; Thanked: 2 times; Followed by:8 members

A OR D??!!

by mehaksal » Mon Aug 06, 2012 11:03 pm

A valid argument is often defined as one in which it is not possible for all the premises to be true and the conclusion false. A circular argument is sometimes defined as one in which one of the premises is identical to the conclusion. From these definitions we can infer that...

(A) Every circular argument is valid as long as its premises are true.
(B) Every valid argument is circular.
(C) No circular argument is valid.
(D) Some circular arguments are valid, and some are not.
(E) Some circular arguments are not valid, and some valid arguments are not circular.

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Source: Beat The GMAT — Critical Reasoning | Mon Aug 06, 2012 11:03 pm

vk_vinayak: Legendary Member; Posts: 502; Joined: Tue Jun 03, 2008 11:36 pm; Thanked: 99 times; Followed by:21 members

by vk_vinayak » Tue Aug 07, 2012 12:05 am

mehaksal wrote:A valid argument is often defined as one in which it is not possible for all the premises to be true and the conclusion false. A circular argument is sometimes defined as one in which one of the premises is identical to the conclusion. From these definitions we can infer that...

(A) Every circular argument is valid as long as its premises are true.
(B) Every valid argument is circular.
(C) No circular argument is valid.
(D) Some circular arguments are valid, and some are not.
(E) Some circular arguments are not valid, and some valid arguments are not circular.

I think A.

According to the stimulus, the definition of Valid sentence: if all premises are true, then conclusion is also true.
Since, in a circular argument conclusion is identical to a premise, it follows that if all premises are true, conclusion must be true. If premises are true and conclusion is also true, it's a valid argument. So, we can say that when all premises of a circular argument are true, it is a valid argument.

- VK

I will (Learn. Recognize. Apply)

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ssidda01: Junior | Next Rank: 30 Posts; Posts: 15; Joined: Wed Nov 10, 2010 7:06 am; Thanked: 1 times

by ssidda01 » Tue Aug 07, 2012 11:40 am

Based on the definition provided for a valid argument, my answer is B.

Valid Argument - A valid argument is often defined as one in which it is not possible for all the premises to be true and the conclusion false. In my opinion this means that we can have either a correct/wrong premise or a wrong/wrong premise with either a correct/wrong conclusion.

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Bill@VeritasPrep: GMAT Instructor; Posts: 1248; Joined: Thu Mar 29, 2012 2:57 pm; Location: Everywhere; Thanked: 503 times; Followed by:192 members; GMAT Score:780

by Bill@VeritasPrep » Tue Aug 07, 2012 3:34 pm

vk_vinayak wrote:
mehaksal wrote:A valid argument is often defined as one in which it is not possible for all the premises to be true and the conclusion false. A circular argument is sometimes defined as one in which one of the premises is identical to the conclusion. From these definitions we can infer that...

(A) Every circular argument is valid as long as its premises are true.
(B) Every valid argument is circular.
(C) No circular argument is valid.
(D) Some circular arguments are valid, and some are not.
(E) Some circular arguments are not valid, and some valid arguments are not circular.
I think A.

According to the stimulus, the definition of Valid sentence: if all premises are true, then conclusion is also true.
Since, in a circular argument conclusion is identical to a premise, it follows that if all premises are true, conclusion must be true. If premises are true and conclusion is also true, it's a valid argument. So, we can say that when all premises of a circular argument are true, it is a valid argument.

Agreed, and good explanation.

The first sentence of the stimulus is a convoluted way of saying that the truth of the premises guarantee the truth of the conclusion.

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