LSAT 78 – Section 1 – Question 14

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Type Tags Answer
Curve Question
PT78 S1 Q14
Necessary assumption +NA
+Hardest 149.45 +SubsectionMedium

Question Stem
We're looking at a Necessary Assumption question. The key phrase in the question stem is "assumption required."

Foundational Skills
This question tests your understanding of how to negate conditional statements. What does it mean to say "If A then B is not always true"? It also tests your understanding of how to use an example to support a the negation of a conditional statement. You just need to show one instance of A and not B.

Aside from logic, this argument also tests your ability to distinguish among the concepts of a promise, an obligation, and an ability to perform an action.

The stimulus starts with the conclusion and it is phrased in the negative. The ethicist concludes "The general principle does not always hold true." Okay, what "general principle"? Read between the dashes. "If one ought to do something, then one can do it." That's the general principle and it's a conditional claim. Before you continue, you have to make sure that you know what it means to say "that does not always hold true" to the conditional claim. That's the lesson on negating conditionals. What is the negation of "if A then B?"

The wrong but perhaps tempting answer is "if A then not B" or "if one ought to do something, then one cannot do it."

The right answer is "A does not imply B" or "ought does not imply can." Another way to say that is "An obligation to do something doesn't automatically mean that you are capable of doing the thing." Fully and correctly fleshed out, this seems like a trivially obvious claim. There are so many things that one ought to do, but that doesn't mean that one can do it. "Ought" is a moral claim. "Can" is a physical claim.

But, we still have to support this somewhat obvious conclusion. Reading the next line in the stimulus, you see that the ethicist wants prove her conclusion by "considering an example." A good exercise is to pause here and ask yourself how you would proceed. How would you prove this conclusion with an example? Since the claim is "ought doesn't imply can" or "A does not imply B," you could support this with an example of a situation where there is an "ought" but there is not a "can." A and not B.

That's abstract. Let's bring it down to earth. Can you think of an "ought" situation? A situation where one ought to perform an action? A situation where one has an obligation to do something? How about this: one ought to financially support one's impoverished parents in their old age. That's the A.

Good. Now add to that situation "not B." How about this: but sometimes, one does not have the financial means to do so. There, that's a clean example of an "ought" (a moral obligation) does not automatically create a "can" (a capability).

Having gone through this exercise, let's now look at what example the ethicist provides. She asks us to suppose that someone promises to meet a friend at a certain time but because of an unforeseen traffic jam, it becomes impossible to do so. Remember, this example should be a situation where there is an "ought" (a moral obligation) coupled with a lack of capacity to carry out the obligation (a "cannot"). So is it?

If you think "yes" then you've already subconsciously taken the bait by supplying the missing assumption. The lack of capacity to do something is present given that it is "impossible" to meet the friend at the promised time. But what about the "ought" or the obligation? Is that present? Note the distinction between this example and the one above where it was explicit that "one ought to financially support one's impoverished parents in their old age." Here, there's just a "promise." So we've spotted one necessary assumption bridge, that "a promise creates an obligation." That's required. And stated explicitly, it seems so obvious, which is why it's easy to overlook. We all know that of course a promise creates an obligation, like what kind of jerk are you if that's not one of your operating moral principles in life? But that's not the point. The point of many necessary assumption questions is precisely to identify and make explicit these implicit assumptions, however foundational they might be to leading an ethical life.

I think this much you can anticipate based on the pure form of this argument. You just have to pay attention to the fact that what you were looking for was an obligation yet what the stimulus gave you was a promise. We need the necessary assumption bridge that "a promise creates an obligation."

Answer Choice (A)
Answer choice (A) is incredibly tricky and I think it has the potential to trap students who understand conditional logic and even to some extent anticipated the missing bridge. Remember, we said that what we're looking for is the explicit statement that "a promise creates an obligation." In conditional form, that's "If one promises to do X, then one has an obligation to do X." In the contrapositive, that's "If one does not have an obligation to do X, then one has not promised to do X." Here now we get very close to the trap in (A). (A) says if one "failed to do something" that one "ought to have done," then one "failed to do something" that one "promised to do." Close in appearance, right?

But quite different in meaning. Not having an obligation to do X is not the same as having (and then failing) the obligation to do X. It's contradictory, in fact. I have no obligation to feed my neighbor's dog. That's not the same as my having (and then failing) the obligation to feed my neighbor's dog. Similarly, not promising to do X is not the same as promising (and then failing) to do X. I did not promise to feed my neighbor's cat. That's not the same as my having promised (and then failing) to feed my neighbor's cat.

Answer Choice (B)
Answer choice (B) puts a hard constraint or limit on what could possibly excuse or relieve a person from the obligation to keep a promise. (B) says that there's just one thing that could do it: an unforeseen traffic jam. Okay, but that damages the argument. According to (B) there is no obligation, because the obligation is excused owing to the unforeseen traffic jam. But if the obligation disappears, then the example becomes worthless. We only cared about the example in the first place because it was supposed to create an obligation. That's why (B) is wrong.

As a side note, think about just how absurd the claim in (B) is. I mean, really, nothing else (aside from the unforeseen traffic jam) can excuse me from the obligation to keep a promise? Like if I get into a car accident and have to go to the ER, that won't relieve me of the obligation to keep my promise?

Answer Choice (C)
Answer choice (C) is similar to (A) in that it's giving off the logical appearance of the bridge we anticipated, but in substance, it's all wrong. Remember, the bridge we need is "a promise creates an obligation." (C) tries to bridge "obligation" to "capacity" or "capability." (C) says that an "obligation" to not do X implies a "capability" to not do X. This claim is actually similar to the original general principle that the ethicist is trying to refute, the general principle that an "obligation" to do X implies a "capability" to do X. For example, an obligation to feed the neighbor's dog implies the capability to feed the neighbor's dog. Here, the X is stated in the negative, an obligation to refrain from doing X implies the capability not do X. Is this claim required? No, it's not. We can falsify this claim and leave the original argument unaffected.

Let's falsify this claim. For example, I have an obligation not to reveal to the Nazi officer that I'm hiding a Jewish family in my cellar. I'd like to think that that implies my being capable of not revealing this. But that's just false. Whether I'm capable or not of revealing this depends on so many incidental factors like how good my poker face is, how good the Nazi officer is at detecting lies, how resilient I am to questioning under torture, how committed I am to fulling my obligations. Obligation simply does not imply capability. Okay, (D) is falsified. But then what? We're still where we were with the original argument. There's still that bridge we identified that needs to be built. The argument is not ruined. It's not even affected.

Correct Answer Choice (D)
Answer choice (D) is the correct answer choice for two reasons. First is that it declares the bridge we needed. It says "The obligation created by a promise..." Good. We know this is necessary. Then it goes on to say something else that I did not anticipate. It goes on to say that that obligation (created by a promise) isn't relieved by the fact that the promise now cannot be kept.

Is this necessary? Yes. It didn't occur to me that an obligation once created can be uncreated. I was simply focused on formally bridging "promise" to the creation of an "obligation." But (D) points out something else just as necessary. That the obligation persists even when it becomes impossible to fulfill that obligation. Indeed that is what the ethicist's example requires. Imagine if (D) were false. That is, imagine if impossibility relieved or excused or unmade the obligation. Then the ethicist's argument is ruined. The example would then contain a situation without an obligation. That example would then become useless to support the conclusion.

Answer Choice (E)
Answer choice (E) does not bridge "promise" to "obligation." It merely says that if some "unforeseen" event "interferes" with the keeping of a promise, then that promise should never have been made to begin with. It's an absurd claim, much like (B), but even if we accept this claim, we get no where on the argument. The consequence of this claim, if we accept it, is just that the promise to meet a friend at a certain time should never have been made to begin with. But the promise was made and the question remains whether that promise made created an obligation. (B) is silent.

More to the point, (B) is unnecessary. We can dispense with this absurd claim without damaging the argument. No, (B), that's just not true. You don't have to judge whether a promise should have been made by looking at whether unforeseen events would interfere with the fulfillment of that promise. You might want to look at whether foreseeable events would interfere. That seems reasonable. Like if you can foresee that you'll be attempting to cross downtown rush hour traffic, then you probably shouldn't promise that the trip will only take 10 minutes. But all of this leaves the argument unaffected. Regardless of whether a promise should have been made to begin with, the fact is that a promise was made and we need to know if that promise created an obligation.

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