Q23 - For each action we perform

[rzaman]

Could someone please walk me through how to approach this problem? I get that it is a sufficient assumption assumption but am not sure of the argument core. What I got was:

(P)
For every action we perform, we can know only some of its consequences
---->
(C)
If an action's being morally right is the same as the action's having the best consequences, we can conclude that in no situation can we know what action is morally right

So the conclusion is basically saying that in no situation can we know what actions have the best consequences and for the author to make that conclusion, the author must have assumed that to know the best consequences we need to all of the consequences, right?

Answer choice C basically says that but it took me a while to figure out what the stimulus is saying. I tried to do this question by diagramming it out and got confused about how to notate the parts and what to link together so I was wondering how someone might approach this question in a more efficient manner. Thanks!

[ManhattanPrepLSAT1]

Sometimes the most efficient manner doesn't involve notation at all. I think the reason you ran into difficulty notating this question is that it's pretty tough and would need to be diagrammed loosely.

A ---> ~KAC
-------------------------------
(MR ---> BC) ---> (A ---> ~MR)


Notation Key: A = action, KAC = know all the consequences, MR = morally right, BC = best consequences

Taking the contrapositive of the sufficient condition of the conclusion yields:

A ---> ~KAC
--------------------------
(~BC ---> ~MR) ---> (A ---> ~MR)

you could rearrange things to make it easier to see the gap...

A ---> ~KAC

~BC ---> ~MR
------------------
A ---> ~MR

Now you can see the gap reads, ~KAC ---> ~BC

Taking the contrapositive, BC ---> KAC

Back into English... "knowing the best consequences requires knowing all the consequences."

Lot's of work, I know, and probably not the most efficient way to work through this one, but there it is visually!

Does that answer your question?

[rzaman]

Thanks so much!! I see what you mean about this question needing to be diagrammed loosely. I have a couple of questions about your diagram. How did you know to take the contrapositive of the sufficient condition? I see that taking the contrapositive of the sufficient condition really makes it clear which parts can be linked and the gap that exists, but I’m worried that it’s not immediately instinctual for me to see that. Would you diagram this question during the test or would you try to reason it out without the diagram?

My other question is if I had decided to diagram the first sentence (For every action we perform, we can know only some of its consequences) as:

A ---> KSC (the S standing for some)

and thereby diagrammed the problem as:

A ---> KSC

~BC ---> ~MR
------------------
A ---> ~MR

Then the gap would be KSC---> ~BC and the contrapositive
BC ---> ~KSC which isn’t equivalent to answer choice c anymore right? Are you not supposed to diagram the first sentence as A ---> KSC and if not, why not?

[ManhattanPrepLSAT1]

How did you know to take the contrapositive of the sufficient condition?

I knew to take the contrapositive of the sufficient condition, because it would help align the necessary portions (~MR).

When you go to piece together an argument like

R ---> T
Q ---> ~P
-----------
P ---> ~R

and you're looking for the assumption. Start by aligning the sufficient and necessary conditions in the evidence and the conclusion:

P ---> ~Q

~T ---> ~R
------------
P ---> ~R

it helps make the gap more obvious.

Are you not supposed to diagram the first sentence as A ---> KSC and if not, why not?

Technically, you're not committing an error in reasoning by notating the information that way, but it's really missing some of the information. That would translate back into English as, "for each action we know some of the consequences." It's missing the crucial limiting factor that we know "only" some of the consequences.

It's not that A ---> KSC is wrong, it's that it doesn't accurately reflect what the sentence is trying to express.

To your final question...

Would you diagram this question during the test or would you try to reason it out without the diagram?

I would try to work through this question on the day of the test without conditional logic, but the location in the section (between 17-23) and the question type (Sufficient Assumption) work strongly in association to suggest using notation. If the assumption didn't jump out at me right away, I'd turn to the notation fairly quickly on this one.

Hope that helps! And let me know if you have any further questions on this one...

[gotomedschool]

C is the only answer choice that mentions the term "best consequences". That is how I approached this question...

faulty approach or no?

[ManhattanPrepLSAT1]

That approach is going to by and large be accurate. There are a few cases where the the correct answer may not contain a key term that appears necessary to tie in. It'll be more accurate when the key term is involved in the conclusion - which is the case here.

For another example check out PT43, S2, Q10 - albeit an easier example.

[zainrizvi]

Why does the "some" used here not include the possibility of all? Our sufficient assumption would no longer be so sufficient I think

[austindyoung]

I have a question,

(A ---> ~MR)

So, the sentence, relative to this diagram, is: in no situation can we know what action is morally right...

That can be adjusted to: in any situation we cannot known what action is morally right.

This would usually yield: S---> ~Know Action is MR

However, as you wrote this also means: A---> ~MR. But we took out the "situation" part and the "know" part.

I just wanted to know how you knew to reduce this to a simpler diagram as you did?

It worked great- and I personally try to stray from having to diagram, but this broke it down really well.

[zip]

Why does the "some" used here not include the possibility of all? Our sufficient assumption would no longer be so sufficient I think

The stimulus says "only some"... Good eye though.

[katken]

Would someone might explaining this problem in prose to complement the diagramming above?

Thanks!
K

[ManhattanPrepLSAT1]

I'll provide some commentary to the notation, no problem. Commentary offered in blue.

A ---> ~KAC (fore ach action we perform we do not know all of it's consequences)
-------------------------------
(MR ---> BC) ---> (A ---> ~MR) (if an action's being morally right depends on it having the best consequences, then for no action can we know whether it is morally right)

Notation Key: A = action, KAC = know all the consequences, MR = morally right, BC = best consequences

Taking the contrapositive of the sufficient condition of the conclusion yields:

A ---> ~KAC
--------------------------
(~BC ---> ~MR) ---> (A ---> ~MR)

you could rearrange things (draw the sufficient condition of the conclusion up into the evidence) to make it easier to see the gap...

A ---> ~KAC
___ --> ____ (there's a gap here)
~BC ---> ~MR
------------------
A ---> ~MR

Now you can see the gap reads, ~KAC ---> ~BC (if one does not know all the consequences, then one does not know all the best consequences)

Taking the contrapositive, BC ---> KAC

Back into English... "knowing the best consequences requires knowing all the consequences."

[sumukh09]

Really great conditional logic explanation of this question, Matt!

I have a question about the part of the stim that says "If an action's being morally right were the same as the action's having the best consequences."

You have this diagrammed as MR ---> BC. When something says it's the "same" as something does that imply that it is the necessary condition of the thing it is equivalent to?

In other words, does "were the same as" introduce a necessary condition?

[raziel]

I don't know if this is the correct way to do it in all problems, but in this problem it seems like you can diagram "the same" as implying an if and only if relationship. Since the argument is postulating that an action being morally right and having the best consequences might be the same, then we can infer that (1) having the best consequences is the morally right action and (2) the morally right action is the is the action with the best consequences.

Everything else works the same as Matt has written because negating A<-->B can result in ~B-->~A or ~A-->~B depending on what we need to prove the conclusion from the evidence given in the passage.

[redcobra21]

(MR ---> BC) ---> (A ---> ~MR) (if an action's being morally right depends on it having the best consequences, then for no action can we know whether it is morally right)

Hey Matt,

Thanks for the helpful explanation. I came across this problem in the Manhattan Grouped by 10 book and thought it was a great reflection of the more challenging questions on the test.

Just a follow-up question if you get the chance though. I'm still a bit confused by how you diagrammed this part. Based on your diagram, it looks like the "MR" in the sufficient part symbolizes "being morally right," but in the necessary part, "~MR" symbolizes "don't know if it is morally right." These seem to be two different things since an action actually being morally right does not seem to be the same thing as "knowing" whether it is morally right. I'm not quite sure how you decided that the two could be diagrammed as the same thing in the conditional logic (other than the fact that it would allow us to connect the various conditional statements), and I feel like I've been burned in other instances of conditional logic by equating two things together that were actually different due to a small nuance. Could you let me know what I'm getting wrong when you get the chance? And thanks in advance!!

[TJG209]

i have a question about the negations used above. is anyone still active on this forum for PT 45?

[BensonC202]

i have a question about the negations used above. is anyone still active on this forum for PT 45?

Here is how I cracked the argument.

Premise:

1. If an action be performed, only some of the consequences of that action be known

2: If an performed action is morally right, that performed action must have the best consequences

Conclusion:

In any situation that we can know the performed action is morally right, it would not be true.

( As I Interpret the conclusion, I know instinctually that the conclusion could be translated to - In any situation that we can know what the action be performed, it must be necessary true that performed action being morally right is under no circumstances )

More refined version - If we know the action be performed, that performed action could be anything but morally right.


*I have been trying not to diagram too much to save times regardless how great and useful diagraming the question could help us out on cracking question.

So, If an action be performed, only some of the consequences of the action be known, then it must necessary true that you know the action be performed. right ?

Hence

If we know the action be performed, then it must be true that we know only some of the consequences of that action.

( A -> B )

+

If we know the action be performed is morally right, then it must be true that we know the action performed has best consequences.

( A -> M ) -> ( A -> BC )

=

If we know the action be performed, then it must be true that performed action, we know of, could be anything but morally right.

( A -> ~M )

Contrapositive of the 2nd premise - If we do not know whether the action performed has the best consequences, we know the action be performed could be anything but morally right

( A -> ~ BC ) -> ( A - ~M )

Apparently, the missing statement is = If we know only some of the consequences of the action performed, then we do not know whether the action performed has the best consequences.


( A -> B ) -> ( A -> ~ BC )

Contrapositive:

If we do know the action performed has the best consequences, we must know all the consequences of the action performed.

( A -> BC ) -> ( A -> ~ B )


I hope it helps !!!

Please let me know if my idea is wrong, and critics be highly appreciated.