Parallel Flaw-SN. The correct answer choice is (D)
The stimulus states that congenial guests and a plentiful supply of good things to eat and drink are sufficient to have a successful dinner party:
Congenial Guests and Success Plenty Good FD
Since Sylvia will have only congenial guests and plenty to eat and drink at her dinner party, the stimulus concludes the party will be a success.
The stimulus is flawed, but not precisely because of formal logic. Congenial guests and good things to eat and drink are sufficient conditions, so the reasoning seems superficially good.
There is actually a detail error. The initial rule mentions plenty of good things to eat and drink, but we only know that Sylvia has plenty of things to eat and drink.
The flaw is that the stimulus fails to be specific about quality when discussing Sylvia's food:
Congenial Guests and Success Plenty ? FD
Answer choice (A): This reasoning is good, and does not involve a similar detail error, so this response is incorrect.
Answer choice (B): This reasoning is poor, but involves a Mistaken Reversal, not a detail error, so this choice is wrong. The stimulus had good logical flow; the error was a mere detail.
Baked Moist and and Husk on Sweet
Moist Baked and and Sweet Husk on
Answer choice (C): This reasoning is perfectly good, so this response is incorrect.
Answer choice (D): This is the correct answer choice. Just like the stimulus, the general logical flow is correct, but the response makes a detail error, because it does not state that Arnold's meat stock is well-seasoned.
Answer choice (E): This reasoning is logically unjustified, but involves a Mistaken Negation, rather than a detail error.
This is the question about congenial guests, correct? This problem is conditional in nature, and the first sentence can be diagrammed as:
Congenial guests + plentiful supply of good things to eat and drink successful dinner party
Because Sylvia then has congenial guests and a plentiful supply of food (but not necessarily good food) and drink, the conclusion is that she will have a successful dinner party. This is a flawed conclusion because the term "good" was used in the first premise but not in the second premise.
Answer choice (C): This is actually valid reasoning; no term is dropped as it is in the stimulus.
Answer choice (D): This parallels the stimulus, and in this answer "well-seasoned" is in the premise but not in the remainder of the answer.
Does that help explain this problem? Please let me know. Thanks!
Congenial guests and a plentiful supply of good things to eat and drink will ensure a successful dinner party. Since Sylvia has prepared more than enough to eat and drink and her guests are all congenial people her dinner party is certain to be success.
...Is ensure a sufficient or necessary condition ? Please diagram out this question for me. I got C but the answer was D. Thank you .
It's important to remember that you can always rephrase conditional statements into If-then sentences. In this case, "ensure" means "the first thing will lead to the second thing". The sentence could thus read:
If you have congenial guests and a plentiful supply of good things to eat and drink, then you are sure to have a successful dinner party.
The trick with both that one and answer choice D is the lack of an important qualifier. Sylvia has congenial guests, and prepared enough to eat and drink...but are they good things that she prepared? They may not be. What if she is a really lousy chef and her food and drink are atrocious?
Answer choice D has the same problem. Arnold's meat stock is not specifically described as "well seasoned", so it might not be, which would invalidate the conclusion.
Is "ensure a successful dinner party" the Sufficient Condition? If so, then I understand why D is correct, but how does C not also contain a Mistaken Reversal as well. Or is it the other way around? If "ensure a successful dinner party" is the Necessary Condition, then where is the flawed reasoning? I would diagram the statements, but I am so confused that I think that would make my question confusing as well. Thank-you.
This is a tricky problem! It came up a few years ago, and in my reply to that question I talked about both answer choices (C) and (D). So, with your question, I first want to refer you to that prior answer above.
I also show the diagram for the "ensure" statement, but let me add here that when you look at that sentence, the way "ensure" is working is that if something ensures another, then it's telling you that the other thing happened. So, in this case, what do you get when you have congenial guests and the plentiful supply? Those two things tell you that you'll have a successful dinner party, and so we put those two things on the sufficient side (you could interpret this as causal as well, and then guest/plentiful supply combination would be the cause).
By the way, I think they threw "ensure" into answer choice (C) simply to make it more deceptively attractive. In Parallel problems, mirroring language like that doesn't automatically mean an answer is incorrect, but when I see it in just one or two answers, I get really suspicious.
I understand the reasoning of the argument, however to me, on a more broad logical reasoning argument, the words "will ensure" seem to denote more of a causal relationship than a conditional one, given their strength.
Essentially, this question is saying: "These two things will make this happen". Isn't that causal reasoning?
The dictionary defines "ensure" as "make certain something will occur" which is what answer choice C says.
I like where your focus is going. Which is to say, one of the key strategies for the LSAT is to look for arguments and immediately determine the whether it is something that is merely conditional, or something about causation. So well done on asking yourself this question. I also love the fact that you went to the dictionary. Law school will love you for it too. But let's get to your question.
Isolating the word "ensure" from the word "will" is not a good idea. Let's look at the way that "will ensure" operates in everyday language: A seatbelt will ensure that you don't die in a car accident. But let's examine that statement. I am telling you that if you get into a head-on car collision then a seatbelt will prevent you from going through the windshield of your car. But what about other types of car accidents? What if you drove into a lake? Would a seatbelt cause you to be saved in that kind of accident? It probably wouldn't. Wearing a seatbelt is merely one of the conditions in not getting killed in a car. Therefore, we cannot say that "will ensure" is a truly causitive phrase either in our everyday life or in this stimulus.
Thanks for the great question and I hope this helps!