I don't like to diagram a question unless I absolutely have to. But when I see "if" in the first premise, and then "if and only if" in the second premise, with "The philosopher's conclusion follows logically if which one of the following is assumed" as the question, then I sharpen my pencil and get to diagramming. Welcome to Section 2, #23, of the June 2007 LSAT. (Note: This is a Sufficient Assumption question. I really want to teach you about Sufficient Assumption questions--they're very learnable! Unfortunately, this particular Sufficient Assumption question is very difficult. If you're relatively new to the LSAT, you might benefit from trying some other questions of this type before tackling this one. Start with the ones that occur earlier in their section.)
The first premise says "an action is morally right if it would be reasonably expected to increase the aggregate well-being of the people affected by it." My diagram of this premise looks like this:
Reasonably expected to increase aggregate well-being --> morally right
NOT morally right --> NOT reasonably expected to increase aggregate well-being
The second premise says "an action is morally wrong if and only if it would be reasonably expected to reduce the aggregate well-being of the people affected by it." My diagram of this premise looks like this:
Morally wrong <--> Reasonably expected to reduce aggregate well-being
NOT morally wrong <--> NOT reasonably expected to reduce aggregate well-being
Note that on the second premise, the arrows go both ways since it says "if and only if." (That's one of the rare things you need to memorize in your LSAT preparation.)
The conclusion of the argument says "Actions that would be reasonably expected to leave unchanged the aggregate well-being of the people affected by them are also right." The question asks us to make this conclusion "follow logically" from the premises. This is a Sufficient Assumption question. On this type of question, we're trying to find one additional premise that, when combined with the evidence we already have, will prove our conclusion. Another way of thinking about this is that we need to build a bridge from the premises that exist to the conclusion we are trying to prove.
Usually on a Sufficient Assumption question, I can predict the correct answer with near certainty. But on this one, I'm stumped. The only premise we have about things that are "morally right" is the first premise: If something increases well-being, then it's right. Our conclusion, unfortunately, is about things that do NOT change well-being. I don't think it would make sense to say "anything that is not expected to change well-being is expected to increase well-being." Technically, if that were true it would prove our conclusion. However, that makes no sense, so I doubt it will be our answer. I have no choice here but to proceed to the answer choices, hoping to find an answer that, if true, would prove our conclusion.
A) I don't see how this is relevant, since we need to link in the idea of "actions that are reasonably expected to leave unchanged the aggregate well-being of the people affected."
B) Hmm. Again, I don't see how this is relevant. How would this connect in the idea of neutral actions? All this answer choice proves is that there isn't any overlap between right and wrong.
C) I can make a case for this one. This answer says there is no middle ground--every action has to be either right or wrong. Since we already know that EVERY morally wrong action MUST be expected to reduce the well-being of the people affected by it (because the "if and only if" arrow goes both ways), then we know that an action that is not expected to change the well-being of those affected by it cannot be a morally wrong action. Okay, and if C is true, anything that isn't wrong has to be right. So I'm pretty sure that C proves our case. I'm going to be pretty happy with C as long as I can get rid of D and E.
D) Who cares? It doesn't matter whether these actions actually exist. What matters is whether these actions, if they exist, are right or wrong. This isn't it.
E) Consequences are entirely irrelevant. C is the only answer that provides a bridge between actions that are expected to leave aggregate well-being unchanged and those actions being "morally right." So our answer is C.