#25 - Essayist: Every contract negotiator has been lied to

[Administrator]

Complete Question Explanation

Must Be True. The correct answer choice is (A)

This stimulus presents several conditional statements which can be linked together. Statements involving "every" or "anyone who" reflect a conditional relationship, the ramifications of which often become clear through diagramming:

If you're a contract negotiator, then you've been lied to by someone.

CN → BLT

If you lie to someone, then you're practicing deception.

LT → PD

If you've been lied to, then you have also lied to someone.

BLT → LT

We can now tie together all of these conditional statements to form the following:

CN → BLT → LT → PD

(So, if you're a contract negotiator, then you've been lied to, so you've also lied to someone, so you've practiced deception)

We can also draw the contrapositive:

PD → LT → BLT → CN

Answer choice (A): This is the correct answer choice. It links the two ends of our master diagram together, starting at the leftmost sufficient condition, and ending with the rightmost necessary condition. In other words, CN → PD: If you're a contract negotiator, then you've practiced deception.

Answer choice (B) From our second diagram, LT → PD, we can only conclude the contrapositive: PD → LT (if you don't practice deception, then you haven't lied to someone). Otherwise, we cannot start any SN relationship with PD. That would be a mistaken reversal. This answer choice is basically saying "Some people who practice deception do not lie to anyone".

Answer choice (C) This statement is invalid because of our second diagram: LT → PD. The second half of that first sentence states that whoever lies to anyone is practicing deception. There's no room for somebody to lie to someone but not be practicing deception.

Answer choice (D) Take a look at our master diagram, again. This answer choice is way too specific; the stimulus never mentioned people who lie to contract negotiators. This should be a warning sign. Plus, our master diagram starts with "If you're a contract negotiator…", not "if you've lied to a contract negotiator".

Answer choice (E) This answer choice is a mistaken reversal of the third diagram: BLT → LT. We can say from the last sentence that if you've been lied to, you've also lied, but we can't reverse that and say that if you've lied, you've also been lied to.

[netherlands]

Hi there PS,

I got this question right - but of course, before doing so got stuck between A and B.

Is "B" wrong because it is a "Could be True" and not a "Must be True"? Basically, it is a rule that the Necessary Condition does not required the sufficient condition - meaning everyone that is practicing deception doesn't necessarily have to be lying to someone.

But it is still a possibility that everyone that is PD'ing also happens to be in the lying to someone category?

Whereas PD is a necessary condition to Contract Negotiators, and therefore it Must Be true?

[netherlands]

I guess basically lack of a sufficient condition is not a must be true, its a could be true.

[Lucas Moreau]

I'm sorry - exactly which question were you asking about? Could you give the lesson number and page number?

[netherlands]

Oh, sorry about that. It was HW Lesson 1 Number 5 page 1-76

[Nikki Siclunov]

You got this right. The premises form the following conditional relationship:

CN Lied to Lie Practice Deception

Clearly, every CN has practiced deception (A). While everyone who lies practices deception, the MR of that statement could be true: i.e. it is possible that everyone who practices deception is lying to someone. This is why (B) is not necessarily true. Remember: the MR and MN are errors in inference-making. They could be true in the context of the original statement.

Does this help?

[netherlands]

Hi there,

Thank you for confirming! It's starting to soak in now what the main principles to follow kind of are:

Conditional Statements and their Contrapositives are the only things that can be proven as Must Be True.

Whereas Mistaken Reversals and Mistaken Negations will always be Could Be True - never must.

[Jon Denning]

That's correct. Very important to keep that distinction--must vs could--in mind, both for LR and for Games.

[rameday]

I am on page 1-76 of the course workbook. My concern is with question 5. My pre phrase for that question was people who lie to CN are deceptive and also the CN who lies to others are also deceptive. That led me to select A as the correct answer. I was torn between A and E though but I ultimately chose A because of my pre-phrase. I am just wondering why A is incorrect and E is correct and how could I have made my pre phrase better?

A

[KelseyWoods]

Hi A,

Answer choice (A) is correct for this question so you actually got it right! Your prephrase was a good one, and led you to the correct answer choice (A).

Answer choice (E) doesn't work because it's a mistaken reversal of one of the conditional relationships in the stimulus. We know that whoever has been lied to has also lied to someone. But that doesn't mean that everyone who lies has been lied to.

Hope this helps!

Best,
Kelsey