@LowriThomas The negation of an A proposition is its O proposition, according to the Modern Square of Opposition. So the negation of (D) is really "some books that give readers pleasure were not intended by the author to have that effect." Your negation uses the word "can" ( which implies the possibility of existence); the correct negation uses the word "some" (which confirms existence).

J.Y.'s explanation is all over the place. The explanation provided in the answer makes no sense. Here's my explanation:

The author's conclusion is the following:

It is NOT the case that: the writing of authors--who write for their readers' pleasure--contains false information.

The discussion of the sales figures is completely irrelevant and is designed to merely waste your time.

Jump to the premise that the author uses to support his conclusion, i.e., the last sentence of the passage:

"If the book were very popular, one could reasonably conclude that it gave people pleasure and therefore that at least some of what is written in the book is not true."

Translated into plain English: popular books, that readers find pleasurable to read, contain some false information.

So let's look at the premise, the conclusion, and try to figure out the missing gap in the argument:

Premise: popular books, that readers find pleasurable to read, contain some false information.

Conclusion: it is NOT the case that the writing of authors--who write for their readers' pleasure--contains false information.

What the readers find pleasurable to read (in the premise) MUST be linked to the authors who, in the conclusion, write for their readers' pleasure.

The necessary assumption?

readers find pleasurable to read → author wrote for readers' pleasure

The clear correct answer choice is (D). Don't pay attention to the other explanations out there; they're far too confusing. Also, the "explanation" provided for (D) is not accurate because it does not properly negate a conditional. The negation of an A proposition is its O proposition, according to the Modern Square of Opposition.

@Kevin_Lin It does--thank you! My second question is regarding a detail that is sometimes important, and sometimes not: Robin states, in the passage, that "If the artifacts were made to last rather than to be quickly discarded, the culture was likely sedentary." However, the correct answer choice doesn't mention anything about an "artifact being made to [have a characteristic];" it just mentions "artifacts that [have a characteristic]." Just because an artifact is made to have a certain characteristic does not imply that the actually has that characteristic; the individuals who made the artifact could have failed in what they set out to do! Sometimes, LSAT questions will be worded so that only the exaimnees that pick up on this detail will be able to answer the question correctly; at other times, like in this instance, such word choice (i.e., an artifact being made to have a certain characteristic vs. an artifact that has that characteristic) has absolutely no relevance to the answer. So, my question: when is it worthwhile to pay attention to such details, and when can they be glossed over and disregarded as part of poor wording by the LSAT question writers?

The fallacy that is committed is that of what logicians define as division.

In the author’s proposed definition, “‘[T]he epistemological beliefs of the medieval epistemologists’" serves a class statement. Medieval epistemologists are presented as a singular class. This is contradicted by the author’s subsequent statement that “if we want to know whether medieval epistemology includes some epistemological claim, we just ask whether any medieval epistemologists believed it.” The author is improperly proceeding from an attribute of “the medieval epistemologists" to that of “any medieval epistemologist[].” In other words, the author is improperly transferring an attribute from a class onto its individual members.

While (D) points out that this class attribute may not be transferable to all of the members of the class—and is thus a valid weakener—answer choice (E) is even stronger: (E) questions the very existence of this class in the first place. In its statement that “[t]here is much debate as to which medieval thinkers, if any, were epistemologists,” (E) opens up the possibility that “the medieval epistemologists” may not even exist. Were this to be the case, the author’s proposed definition—which depends on the existence of a class collectively known as “the medieval epistemologists”—simply cannot be valid.

The author states that “the solution is to define medieval epistemology simply as ‘the epistemological beliefs of the medieval epistemologists.’” How can such there by any “epistemological beliefs of the medieval epistemologists” if there are no members of the class that the author collectively references as “the medieval epistemologists?” 7Sage is mistaken in its explanation, which states that (E) is correct because “[i]f we don’t know who medieval epistemologists were, then we don’t know whose beliefs we should include as part of medieval epistemology.” The reason (E) is correct is notbecause of its statement that “[t]here is much debate as to which medieval thinkers … were epistemologists.” It is because it states that “[t]here is much debate as to which medieval thinkers, if any, were epistemologists.” The possibility that there may not be any medieval epistemologists significantly weakens the author’s argument, which depends upon the existence of at least one medieval epistemologist.

@hannahhuynhYour summary of the historian’s solution in the left column goes beyond the stated explicit premises. When you state that an “opposite idea is also part of medieval epistemology,” you are misinterpreting the last sentence to imply the following:

"[I]f we want to know whether medieval epistemology includes some epistemological claim, we just ask whether any medieval epistemologists believed it. If any did, it is part of medieval epistemology; if any medieval epistemologists believed the opposite, then that opposite claim is also part of medieval epistemology." The inclusion of “also” is simply not supported by the historian’s premises: nowhere in the historian’s argument is there any implication that "this is okay.” The historian does not even consider the possibility that some medieval epistemologists held beliefs that other medieval epistemologists opposed.

It is important to note that the quantifier "any" includes the possibility of "all." In this case, it is possible—in fact, it is likely—that the historian’s use of "any" implies "all.” It appears that the historian believes that all medieval epistemologists have the same beliefs. After all, the historian is attempting to “produce a definition that would help to determine what should and what should not be included in [medieval epistemology].” Definitions, by their very nature, have some degree of precision—and historians have struggled to define medieval epistemology due to their inability to achieve this sort of precision.

In response, the author proposes “to define medieval epistemology simply as ‘the epistemological beliefs of the medieval epistemologists.’” This does not imply that the author believes that it is even remotely acceptable for medieval epistemology to include opposing beliefs! In fact, this appears to be the exact problem that author is attempting to address. After all, if medieval epistemology were to be that imprecise in its set of beliefs, then defining medieval epistemology would have never been a challenge in the first place! If medieval epistemology were to be so fluid that “X” and “not X” were beliefs that were of equal validity to the study of medieval epistemology, then it is impossible to imagine why there has been such a failure—among intellectual historians—to define the set of beliefs that comprising this field of study.

Lastly, the notion that “X” and “not X” are of equal validity—to any field of study—is one that simply fails as a matter of common sense. How can the opposite of a given claim be just as valid as the claim itself? As a concrete, practical example: how can the beliefs that “Jesus Christ existed”—and that “Jesus Christ never existed”—both be equally valid?

The key to the correct answer to this question is not the fact that (D) would not weaken the historian’s argument—or, as you propose, even serve to strengthen the historian’s argument. It is the fact that there is another answer choice would weaken the argument to a greater extent.

@LowriThomas But aren't you just making the case that (B) merely meets the minimum threshold required for a necessary assumption? And isn't the question asking for a sufficient assumption that would justify the conclusion given the premises? Shouldn't the correct answer--in the words of the LSAC's A Guide to Logical Reasoning Questions (in The Official LSAT SuperPrep)--"produce a[] conclusive argument, that is, an argument with no gaps in its support for the conclusion?"

@prestonbigley759 Your distinction between "implementing ideas" and "carrying out ideas" is irrelevant. The final sentence of the passage states that, if the employer utilizes the approach that the sociologist proposes, "the ideas employers will want to try will be implemented more quickly and effectively." The distinction you propose is simply inconsistent with the passage's final sentence. When the passage states that "the ideas employers will want to try will be implemented," who is performing the "implementation"--is it the employees or the employers? Obviously it is the employees; otherwise, the passage's final sentence would be identical to stating that "the ideas employers will want to try will be implemented by the employers"--a notion that is clearly nonsensical.

Rather, the passage's final statement--that "the ideas employers will want to try will be implemented more quickly and effectively"--is synonymous with: "employees will implement employers' desired ideas more quickly and effectively" and "employees will carry out employers' desired ideas more quickly and effectively." The passage therefore equates "implement[ing] ideas" with "carry[ing] out ideas," and further states that both actions are those that are performed by employees. The distinction between the role of employers in these ideas is that they are the ones that generate these ideas. They do not carry out these ideas nor do they implement these ideas. This is not a matter of opinion; it is a conclusion that logically follows from the final sentence of the passage.

Given the last sentence of the passage, the meaning of (C) be unaffected if the answer choice had been worded to state that "Employees are more likely to carry out ideas ..."

@apol640955 You're overlooking the fact that hindsight is always 20/20. He knows what the correct answer is PRIOR to formulating his explanation--ANYONE can do that! But I find it interesting how THERE HAS NEVER BEEN A TIME WHEN HE DISAGREED WITH THE REASONING BEHIND AN LSAT QUESTION. Do you honestly think that someone who thinks of himself as the most knowledgable LSAT tutor would REALLY find NO ISSUE with ANY LSAT QUESTION?! In my opinion, the best LSAT tutors I've worked with are those that acknowledge when a question is poorly written and when they can't explain the correct answer in a way that they themselves would find satisfactory. For example, see his explanation to PT114.S2.Q26--he has clearly made an unfounded assumption (i.e., that the employer mentioned in the question is acting in a campaign to deceive their employees) that even the brightest test-taker would NOT be willing to make UNLESS they knew what the correct answer was and they were tasked with formulating an explanation to "fit" that correct answer.

This question does not make sense logically. And J.Y.'s "explanation"--which he obviously formulated after being told what the correct answer choice is--clearly exemplifies signs of 20/20 hindsight.

In order for anyone to get this question correct, you MUST make the nonsensical assumption that that the employers (and the sociologist, who is offering them a strategy for quick and effective results) were NOT acting in good faith and, in fact, engaging in (and advocating) effective trickery in dealing with their employees. This is an assumption that is simply neither implied by the premises nor consistent with rational thought.

Answer B presupposes employers inclined to conduct a “nonthreatening dialogue that emphasizes positive contributions of the employee," while ultimately concealing their true motive and in fact ignoring the employee's contributions and implementing the original, resented “ideas employers want to try,” unaltered by any substantive discussion with the employees, presumably having hoodwinked them into falsely believing that “they have participated in generating” those implemented ideas (as B would have it). Will the employees really be this docile, so that these ideas can be implemented “quickly and effectively”? Will they not notice that their participation in the dialogue was for nought? For B to be valid one has to assume that the sociologist is suggesting deception (or at least high-handedness) as an effective managerial strategy. 

My question: what is the support for this assumption?

My explanation for why (C) is better supported than (B):

B mentions ideas “that they believe they have participated in,” while C specifies, in addition, that the participation involved a “dialogue” (a bilateral discussion, presumably with the employer), which more closely follows the sociologist’s scenario: “a non-threatening dialogue” (between employer and employees). In B the ideas are ones “they believe they have participated in generating,” which may or may not have involved a dialogue with the boss—they could have been generated unilaterally, in a conclave among just the employees.

Which brings me to my 2nd question: what is wrong with my explanation as to why (C) is more supported by the passage than (B)?

Responding, in part, to 7SageTutor: See attached screenshot, from PT120, Section 4. The explanation to the "trap" incorrect answer is that the answer is incorrect because it "confuses sufficient and necessary conditions."

Applying this identical explanation would make the "correct" answer to THIS question (in PT158) a "trap" answer choice that is actually INCORRECT.

Firstly, your statement saying "I like to ask myself 'If person A believes everything that he's saying, what else does person A have to believe?'" does NOT apply:

Robin's premise: "If the artifacts were made to last rather than to be quickly discarded, the culture was likely sedentary."

Robin's conclusion: "Archaeologists can study the artifacts left by ancient cultures to determine whether they were nomadic or sedentary."

You state that if Person A believes that Robin's premise is correct, that Robin's conclusion is correct, AND that Robin's conclusion is adequately supported by Robin's premise, this would NOT imply, as you indicated in your explanation, that Person A "he HAS to be committed to saying that artifacts not made to last means you're nomadic."

Rather, the correct way to phrase what Person A would HAVE to believe is: "If the artifacts were made to be quickly discarded ("X")rather than made to last ("Y"), the culture was likely nomadic." Since we're talking about what Person A HAS TO BELIEVE: given Robin's premise that "If the artifacts were [X] rather than [Y], the culture was likely sedentary," Person A MUST believe that "If the artifacts were [Y] rather than [X], the culture was likely nomadic."

Equating an artifact that was "made to be quickly discarded" with an artifact that was "not durable" is an assumption that Person A does NOT HAVE to make: just because something was "made to be disposable" does NOT imply that something was "not durable": for example, N95 masks are certainly "made to be quickly discarded." In fact, manufacturers advise AGAINST using an N95 for more than one interaction. But just because N95s are "made to be quickly discarded" does NOT imply that N95s are "not durable." Rather, the OPPOSITE is true. N95s ARE durable; they are able to withstand 95% of all particulate matter, they are made to form a nearly impenetrable seal around the wearer's mouth and nose to the point that an uninfected person wearing an N95 can safely interact with an infected person and yet have a very low likelihood that he/she will contract this highly-contagious virus (one that the wearer would be at a significantly higher risk for contracting absent the N95 mask). This is just one example of the fact that an item "made to be quickly discarded" is NOT equivalent to an item that is "not durable." Simply put: something "made to be disposable" does NOT imply that it is "not durable." In other words, manufacturers of items that are to be disposed of after very short-term use does NOT imply that these items are not durable. For, if these WERE equivalent, the premise on which Robin relies to support her conclusion would have been: "If the artifacts were durable rather than non-durable, the culture was likely sedentary" OR simply "If the artifacts were durable, the culture was likely sedentary."

Secondly, with respect to your statement that "Robin's claim that 'If the artifacts were made to last as opposed to quickly discarded, then the culture was likely sedentary.' [is] not expressing a sufficiency-necessity relationship. Robin is saying that the durability of an artifact is a clue about the kind of culture that made it."

The answer choice does NOT state anything about a strict sufficiency-necessity relationship; rather, the answer choice states that "it is reasonable to assume that a culture ..." That the answer choice refers to what Robin would "reasonably assume" is consistent with Robin's statement, in the passage, that the durability of artifacts (or lack thereof) is an indication that "the culture was likely sedentary." That her statement indicates that something is "likely" to be the case under a given condition IS CONSISTENT with the answer choice's "reasonable assumption."

However, Person A would HAVE to believe the following:

Robin's conclusion that "Archaeologists can study the artifacts left by ancient cultures to determine whether they were nomadic or sedentary," implies that the "likely" condition that is stated in her premise is so likely that it is conclusive. (Recall that "likely" includes the possibility of "certainly," just as "some" includes the possibility of "all."). Otherwise, her conclusion would have contained indicators that do NOT indicate certainty: i.e., she would have stated that ""Archaeologists can study the artifacts left by ancient cultures to reasonably determine whether they were likely to be nomadic or sedentary." That Robin's premise expressing likelihood (expressing a conditional relationship where the sufficient condition implies that the necessary condition is likely) leads her to reach a conclusion that does not contain any indication of likelihood logically implies that she has interpreted her sole premise (which she uses to support her conclusion) to be sufficient, despite its indication of likelihood. Person A would therefore HAVE to believe that Robin has assumed that her premise completely supports her conclusion; this assumption is that Robin intends the "likely" condition she expresses in her premise ("... the culture was likely sedentary") to be a sufficiency-necessity relationship. That is, Robin infers--whether fallaciously or not--that "likely" implies "definitely." Person A, to believe her conclusion, MUSTmake the same "leap" that Robin makes. Simply put: the phrasing of Robin's statement in the passage DOES logically imply that the premise is to be interpreted as a sufficiency-necessity relationship.

Yet, even if this is not the case, the premise could still be interpreted through if/then conditional logic in the following sense:

The SUFFICIENT CONDITION is "artifacts were made to last rather than to be quickly discarded."

The NECESSARY CONDITION is "the culture was likely sedentary."

In other words: Artifacts made to last and NOT quickly discarded => Culture is likely sedentary

The contrapositive, which must also be true, is: Culture is NOT likely sedentary => Artifacts made to be quickly discarded and NOT made to last

The answer choice does NOT reflect this conditional relationship but rather indicates its converse: "it is reasonable to assume that a culture whose artifacts were not durable was nomadic" is equivalent to saying that: "it is reasonable to assume [a conditional relationship]," and that the "conditional relationship" is: Non-durable artifacts => Culture was nomadic.

Person A would not be committed to believing that this conditional statement is "reasonable to assume." The ONLY conclusion that Person A must believe--if Person A were to believe that Robin's premise provides conclusive support for her conclusion--is Robin's conditional statement itself, as well as its contrapositive, i.e., that it is "reasonable to assume" that if a culture were NOT sedentary (i.e., nomadic), its artifacts were made to be quickly discarded. This is not the "reasonable assumption" that is stated in the answer choice: rather, the answer choice states that the converse ("a culture that was not nomadic was one whose artifacts were made to be quickly discarded" is a reasonable assumption).

Can you provide justification for this answer choice being correct despite the various factors I've listed above? And despite the fact that the attached question--from PT 158--relies on the same reasoning that would lead a test-taker to ELIMINATE the correct answer choice in the subject question?

Here is another --even stronger--reason to doubt the inference that Robin would AGREE with (B):

It is also worth noting that the false dichotomy expressed in both Robin's conclusion and the inference that one must draw from the supposed correct answer choice:

The argument is based on the implied premise that it is not possible for a culture to have both artifacts that are "made to last" and those that are "to be quickly discarded." In fact, this is more-than-likely to be the case! What kind of culture produces only items that are durable? In every single culture that exists at present, the production of items that are "made to last" occurs while the production of items that are "to be quickly discarded" also occurs! It would be ridiculous for a culture to only produce items that are "made to last" or only items that are "to be quickly discarded." Robin's argument is severely flawed because it fails to address this possibility. And because it fails to address this possibility, it cannot be assumed that her premise and her conclusion logically imply that "it is reasonable to assume that a culture whose artifacts were not durable was nomadic." An equally-valid possibility could be that "it is reasonable to assume that a culture whose artifacts were both made to last and to be quickly discarded was nomadic, but only if the former outnumbered the latter." Or one could draw the conclusion that it is "reasonable to assume that if there exists at least one artifact that was made to be quickly discarded, that culture was nomadic--even if that culture also left behind artifacts that were made to last." Or one could draw the conclusion that it is "reasonable to assume that if a culture whose artifacts were made to last were equivalent, in number, to artifacts that were made to be quickly discarded, that culture is sedentary." The supposed "correct answer" assumes that, because the premise states that "artifacts were made to last rather than quickly discarded," it MUST mean that ALL of these artifacts being referenced MUST be made to last OR to be quickly discarded. The conclusion does not contain any sort of a dichotomy. It only says that "artifacts left by ancient cultures" can determine whether that culture was nomadic or sedentary. So the premise that "if the artifacts were made to last rather than to be quickly discarded, the culture was likely sedentary" COULD be interpreted in the sense of "at least one artifact," "few artifacts," "most artifacts," or "all artifacts." Of these possibilities, the last possibility is LEAST likely, as it would imply a false dichotomy. But, in order for the answer choice to be correct, it MUST be assumed that EITHER all artifacts are made to last OR all artifacts were made to be quickly discarded--and that it is NOT POSSIBLE for a culture to leave behind artifacts of one kind and also leave behind artifacts of the other. This is too sweeping of an assumption to draw.

I think I've made my case that it cannot be inferred that Robin would agree with "B." Kendall would certainly disagree with it. But Robin may agree with it, may disagree with it, or may be undecided.

Of the remaining answer choices, the only one that makes sense is answer choice (E). Kendall's statement implies that the artifacts that anyone makes is determined by the materials made available to them. The phrase "a people" does NOT imply "people of the SAME culture." It could mean people of the same country. Or people of the same race. Or people of the same religion. But NOT NECESSARILY people of the same culture. So the leap that answer choice (E) makes--i.e., it makes the unwarranted assumption that the phrase "a people" in "what artifacts a people make" MUST be interpreted to imply "people of the SAME culture"--is TOO FAR of a leap that goes BEYOND with what can reasonably be inferred from her statement. On this basis ALONE, Kendall would DISAGREE with (E). The ONLY implication that Kendall's statement could possibly make is that "studying artifacts left behind by a certain group of people can reveal a great deal about those people." This group could be characterized by similarities that DO NOT NECESSARILY include culture; perhaps these people are grouped together because they share the same ideology, or they are of the same political party, or because they share the same habitat, or because they share the same race. Thus, Kendall would DISAGREE with (E) since the answer choice takes for granted that the "people" to whom Robin refers MUST share the same culture rather than some other attribute. Robin would clearly AGREE with (E). So there's your correct answer.

Please explain why this reasoning is faulty and why (B)--which confuses a sufficient condition with a necessary condition and, ON THOSE GROUNDS ALONE, is flawed in its interpretation of Robin's statement--IS somehow the correct answer choice, despite the CLEAR faulty logic that the answer choice contains and the presence of an answer choice that does NOT commit a logical flaw OF ANY SORT. Given these two answer choices, WHY would ANYONE pick the answer choice that CLEARLY commits a logical flaw (i.e., the obvious "confusing a sufficient condition with a necessary condition" a.k.a. "mistaken converse") OVER the answer choice that DOES NOT COMMIT AN ERROR IN REASONING OF ANY SORT?!

Also, if (B) were correct, then the correct answer choice for the attached question (from PT 158) could be (E). After all, if (B) CANNOT be ruled out due to its failure to state the contrapositive of an if/then claim, then why should (E)--in the attached question--be ruled out on those grounds?!

This technique pretty much describes the rule of replacement in formal propositional logic called EXPORTATION.

i.e., [p --> (q --> r)] is logically equivalent to [(p AND q) --> r]

In other words, the "domain" is p. The given statement is, "if p, then q if r." In the "domain" of p, the statement can be simplified to "q if r." In other words, [p --> (q --> r)]. Re-stating this conditional statement WITHOUT "kicking it up to the domain" would yield: "if p AND q, then r," or, in other words, "[(p AND q) --> r]."