Only computer scientists understand the architecture of personal computers, and only those who understand the archite...

Nina July 6, 2014

Question breakdown

I am having a hard time understanding why B is the correct answer. I see that the conclusion is diagrammed: Appreciate advances in technology - > Computer scientist However this cannot be true, because it is arguing that if the sufficient 2nd premise: Appreciate advances in technology to conclude that the necessary clause in first premise: computer scientist. You cannot simply go back.

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Mehran July 12, 2014

Let's diagram the argument.

"Only computer scientists understand the architecture of personal computers."

Remember that "only" introduces a necessary condition.

PR1: UAPC ==> CS
not CS ==> not UAPC

"Only those who understand the architecture of personal computers appreciate the advances in the technology made in the last decade."

PR2: AAT ==> UAPC
not UAPC ==> not AAT

"It follows that only those who appreciate these advances are computer scientists."

C: CS ==> AAT
not AAT ==> not CS

What can we properly infer from these premises? We can connect PR2 and PR1 like so:

AAT ==> UAPC ==> CS to conclude: AAT ==> CS.

The argument, however, has used the necessary condition to conclude the sufficient condition (i.e. CS ==> UAPC ==> AAT).

Remember, don't just reverse; you must always switch the variable AND negate. "CS" is the necessary condition of the first principle rule. Thus, we cannot infer anything else from it.

If you look at the necessary condition of PR1 and its contrapositive, you see that a viable option is to have a computer scientist who does not understand the architecture of personal computers. We know from PR2 that if you do not understand the architecture of personal computers, then you do not appreciate the advances in technology made in the last decade. Therefore, there can be a computer scientist that does not appreciate the advances in technology made in the last decade.

So, answer choice (B), "The argument ignored the fact that some computer scientists may not appreciate the advances in technology made in the last decade," correctly identifies the flaw in the argument.

Hope that helps! Please let us know if you have any other questions.

knoxygirl April 25, 2017

I still don't understand why it is B. The flawed reasoning doesn't say all computer scientists appreciate architecture.

Mehran April 27, 2017

@knoxygirl the conclusion says "only those who appreciate these advances are computer scientists."

"Only" introduces necessary condition so this would be diagrammed as follows:

CS ==> AAT
not AAT ==> not CS

But as mentioned in the comment above, this is the reverse of what you can actually properly conclude from the premises, i.e. AAT ==> CS.

Hope this helps! Please let us know if you have any other questions.

kdehoyos August 29, 2018

I keep getting confused with diagramming "only" . I understand that it introduces the necessary condition, but aren't we supposed to negate the sufficient condition as well as a part of the two rules when diagraming "only"?
for this questions I diagramed the first sentence of this question as:

not UAPC==> CS

Max-Youngquist August 30, 2018

@kdehoyos you are correct that you negate the sufficient condition as part of the contrapositive, however here you have negated the sufficient condition without also negating the necessary condition and reversing the variables.

The correct diagram is:

UAPC ==> CS
not CS ==> not UAPC

It seems here like you possibly combined aspects of the original statement with aspects of its contrapositive. I hope that helps!

Maybeillgetlucky March 16, 2019

How is that a viable option? PR1 contrapositive indicates that if you're NOT a computer scientist (so, not "you are a computer scientist) that doesnt understand the architecture of a personal computer and therefore cannot appreaciate advances in technology.

Bluebell7612 April 30, 2019

I found the analogy that Mehram used in the lesson for this chapter of taking the LSAT being necessary for law school helpful for this question
LAW SCHOOL - -> LSAT
But not everyone who takes the LSAT will go to law school :)

Ravi May 1, 2019

@Maybeillgetlucky,

(B) captures the flaw of the argument, which is confusing a sufficient
condition for a necessary one.

We have

App - >UAPC - >CS

The conclusion of the argument is

CS - >App

This is not a logical conclusion. Not all computer scientists have to
appreciate the advances that have been made. Rather, the correct
conclusion is actually if you appreciate the advances, then you must
be a computer scientist

CS - >App

Thus, it's possible that there are some computer scientists who do not
appreciate the advances.

Does this make sense? Let us know if you have any other questions!

Ravi May 1, 2019

Great point about the analogy, as well! It looks like you have strong understanding of it :)

NinahBinah April 8, 2020

I saw the flaw as circular reasoning. The term "only" is used many times and each time I took it to introduce a necessary condition.