If and Only if Principles

[secretad22]

I know that you guys remember the infamous principle question about "a statement is wholly truthful only if it is true and made without deception."

The other part of the moralist's statements was that:


Deceive or Refrained from Clarifying ---> Lie

So our two principles was that one and...

WT ---> T and ~D

The key to acing this question was knowing that you could not conclude what was wholly truthful. You could also not conclude what was not a lie.

I understand that situation but I am having trouble with a similar concept.

Here is a theoretical problem:

"The police officer shot a person that clearly was without a weapon. That police officer was rightfully punished."

What principle would help to justify the officer's actions?

Let us say that you eliminate all but two answers and these are the ones you are left with during the test.

A) An officer should be punished only if the officer shot a person that clearly was without a weapon.

B) An officer should be punished if the officer shot a person that clearly was without a weapon.


A) Should be punished ---> Officer shot person without weapon

B) Officer shot person without weapon ---> Should be punished

I feel that B is correct but I do not know what to make of choice A.

My question is can we have a sufficient condition of should be punished in this case? Could a principle be established by starting off with the prescriptive language in the sufficient spot?

[ManhattanPrepLSAT1]

Great question! And this gets right to the heart of principle questions.

Suppose you have some evidence: A, and some conclusion B. We can set that up in notation as such.

A
---
B

A principle that would justify the argument would need to establish a conditional relationship that says if the evidence is true, then the conclusion is true A ---> B. Now it would also work to express that principle in the form of its contratpositive ~B ---> ~A.

But any other relationship between A and B would not work. So these would not work:

B ---> A
~A ---> ~B
A ---> ~B
~A ---> B

For your example we would have:

A police officer shot an unarmed person
-------------------------------------------
The police officer was rightly punished

A) Should be punished ---> Officer shot person without weapon

B) Officer shot person without weapon ---> Should be punished

Answer choice (B) would bridge the gap but answer choice (A) would reverse the logic. Reversing the logic is one of the most common ways the LSAT will create incorrect answers on Principle Support questions.

Does that answer your question?

[secretad22]

Yes it does. Thank you!