Critical Reasoning

Identify the information which points to a flaw in the argument below:

Thomas Edison made a vow, when he was a young child, that as an adult he would work with machines. Humanity should feel fortunate, because had Edison not made that vow, he would never have invented important machines such as the phonograph, movie projector, and lightbulb.

(A) Other inventors of famous machines never made the same vow Edison made.
(B) Thomas Edison may have invented things other than machines had he not made his vow.
(C) Thomas Edison only invented machines that he dreamed up while still a child.
(D) Thomas Edison may have become an inventor of machines even without making a vow as a child.
(E) Edison's vow only referred to his working with machines, but not necessarily inventing them.

Why D Or E..Plz put reasons.

We have to find out the flaw in the argument

Option D just states the information, E seems more appropriate

P.S btw I would have gone with A

A seems perfect to me. It suggests that vow is not at all important for a inventor

A close call between option A and E. I would go for E because it directly affects the argument, i would not go on to think what some other machine inventors did, and hence rule out A.

Do let us know the answer to this....

anchit wrote:A close call between option A and E. I would go for E because it directly affects the argument, i would not go on to think what some other machine inventors did, and hence rule out A.

Do let us know the answer to this....

The first statement states that Edison intends to " work" with machines. Whereas the following statement , takes that as a cue and goes a far extent that he intended to "invented".

There is certainly a degree of "scope shift".

Now that we have been asked to identify the flaw. So by default , scope shift is a "flaw".

So pick E.

Why not A??

A comes under the category of "out of scope" .Statement 1 & 2 deals only with Edison. So dragging "other inventors" in to our discussion is "out of scope & redundant".

I believe E gives us the logical flaw in the argument.


What is the OA?

I maybe completely wrong but here goes..

I think E can be eliminated based on the fact that if he invents the machine, he has to "work with it". It probably got to do with the interpretation of those words.

I would pick D because it is possible that he took a vow not to work with machines but also took another one to invent them

If D is correct then I will try to explain it logically with a diagram, if it is not then I will go take a break!

+1 for E

reason as stated above

logical flow only comes if E were true.....that working with machines is considered as working on inventions

OA D.

My thinking went like this

Structure of the argument:
TE (childhood) made a vow.
without that vow the invention of the machines would not have been possible.

So in effect the argument says vow caused invention.

This is apparently ignoring a lot of other reasons for the invention.
So, the flaw in the argument should address the fact that there is no necessary relation between taking the vow and inventing the machine.

And D does this.

Though backtracking the reasoning is easy I thought the reasoning might help..

very good ques.... Nikhil...

can u plz tell us source of such ques...

siddus wrote:I maybe completely wrong but here goes..

I think E can be eliminated based on the fact that if he invents the machine, he has to "work with it". It probably got to do with the interpretation of those words.

I would pick D because it is possible that he took a vow not to work with machines but also took another one to invent them

If D is correct then I will try to explain it logically with a diagram, if it is not then I will go take a break!

my reason for eliminating E is that it uses the word ONLY.

We cannot infer that " Edison's vow only referred to his working with machines, but not necessarily inventing them."

But I still cant figure out why D is right.

Siddus can you please share your diagram..

Nikhil what is the source of this tricky question ?[/b]

martin.jonson007 wrote:very good ques.... Nikhil...

can u plz tell us source of such ques...

KNEWTON practice test..

Right, now as vijay_venky has correctly pointed out this question is a cause-effect type.

The premise states that -


(Cause) Take a vow --------> (Effect) Works with machines

The conclusion states that -

(Cause) Does not take a vow --------> (Effect) Does not work with machines

So its basically saying that if the cause does not occur the effect does not occur. This is a common error in cause-effect reasoning - Failure to consider an alternate cause for the effect. It is possible that there are other reasons why Edison invented the machines, maybe because he wanted to help humanity. So even if had not taken a vow it would still have been possible that he invents the machine. By negating the premise in the conclusion, we are limiting the effect to a single cause (the vow).

Option D addresses this flaw correctly. Another possible answer which would mean the same thing could look something like -

"fails to exclude an alternative explanation for the observed effect"

As for E, I think that in the argument the words, "working with machines" could mean anything from inventing the machines to fixing them or even designing them. This is my interpretation, maybe the experts can shed some more light on this.

I was able to solve this one because I had seen a similar question before. I have posted it here for your reference -

To become an expert on a musical instrument, a person must practice. If people practice a musical instrument for three hours each day, they will eventually become experts on that instrument. Therefore, if a person is an expert on a musical instrument, that person must have practiced for at least three hours each day.

Which one of the following most accurately describes a flaw in the reasoning above?

(A) The conclusion fails to take into account that people who practice for three hours every day might not yet have reached a degree of proficiency that everyone would consider expert.
(B) The conclusion fails to take into account that practicing for less than three hours each day may be enough for some people to become experts.
(C) The conclusion fails to take into account that if a person has not practiced for at least three hours a day, the person has not become an expert.
(D) The conclusion fails to take into account that three consecutive hours of daily practice is not recommended by all music teachers.
(E) The conclusion fails to take into account that few people have the spare time necessary to devote three hours daily to practice.

kaulnikhil wrote:

martin.jonson007 wrote:very good ques.... Nikhil...

can u plz tell us source of such ques...

KNEWTON practice test..

Thanks!