Can a conclusion be based on a flawed premise, especially : GMAT Critical Reasoning (CR)
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# Can a conclusion be based on a flawed premise, especially

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Director
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Can a conclusion be based on a flawed premise, especially [#permalink]

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07 Jul 2011, 23:57
Can a conclusion be based on a flawed premise, especially when the premise is a sub-conclusion.

For example, in the following stimulus (taken from PowerScore Critical Reasoning Bible), the main conclusion ("However, this characteristic is actually quite common.") is supported by several premises including a sub-conclusion ("Thus plankton cause the surface of the earth to be cooler and this benefits the plankton."). I believe that the sub-conclusion is flawed because there's the speaker didn't proved that the cooler surface of the earth benefits the plankton.

Here's the stimulus:

It is well known that many species adapt to their environment, but it is usually assumed that only the most highly evolved species alter their environmentt in ways that aid their own survival. However, this characteristic is actually quite common. Certain species of plankton, for example generate a gas that is converted in the atmosphere into particles of sulphate. These particles cause water vapor to condense,thus forming clouds. Indeed, the formation of clouds over the ocean largely depends on the presense of these particles.More cloud cover means more sunlight is reflected, and so the earth absorbs less heat.Thus plankton cause the surface of the earth to be cooler and this benefits the plankton.

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Re: Can a conclusion be based on a flawed premise? [#permalink]

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08 Jul 2011, 00:22
nonameee wrote:
Can a conclusion be based on a flawed premise, especially when the premise is a sub-conclusion.

For example, in the following stimulus (taken from PowerScore Critical Reasoning Bible), the main conclusion ("However, this characteristic is actually quite common.") is supported by several premises including a sub-conclusion ("Thus plankton cause the surface of the earth to be cooler and this benefits the plankton."). I believe that the sub-conclusion is flawed because there's the speaker didn't proved that the cooler surface of the earth benefits the plankton.

Here's the stimulus:

It is well known that many species adapt to their environment, but it is usually assumed that only the most highly evolved species alter their environmentt in ways that aid their own survival. However, this characteristic is actually quite common. Certain species of plankton, for example generate a gas that is converted in the atmosphere into particles of sulphate. These particles cause water vapor to condense,thus forming clouds. Indeed, the formation of clouds over the ocean largely depends on the presense of these particles.More cloud cover means more sunlight is reflected, and so the earth absorbs less heat.Thus plankton cause the surface of the earth to be cooler and this benefits the plankton.

Thank you.

Hi Nonameee,
Yes conclusion can be based on a flawed premise. I think when solve a weaken CR question what we intend to do is to prove the conclusion is based on a flawed or insufficient premise by choosing an addition premise from the options given.
And in the stimulus you have given, it says “Certain species of plankton” but then conclusion is generalized and is flawed.
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Ranjith Ramachandran

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Re: Can a conclusion be based on a flawed premise? [#permalink]

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08 Jul 2011, 00:29
Ranjith, thanks for your reply. You're right. Actually, I've been investigating this question myself and what I have found out is that, as you said, a conclusion can be based on flawed premises. In fact, premises must ALWAYS be considered to be TRUE on the GMAT.
Re: Can a conclusion be based on a flawed premise?   [#permalink] 08 Jul 2011, 00:29
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