LSAT Logical Reasoning : Assumption

Example Questions

Example Question #21 : Assumption

Magazine article: Multivitamins seem to be taken mostly by the people who do not need them. Studies have shown that among those who take a multivitamin at least once a week, over 70% reported that they also eat, on average, the recommended daily allotment of fruits, vegetables, and whole grains. As one researcher put it, this is like “getting the same vaccination twice.” For these people, the multivitamin is simply not necessary.

Which one of the following is an assumption upon which the magazine article’s argument depends?

The amount of people who both take multivitamins regularly and eat the recommended daily allotment of fruits, vegetables, and whole grains is greater than the amount of people who do only one of those activities.

Those who participated in the studies cited by the magazine article did not taint their diets by eating a large amount of fattening and sugary foods.

Multivitamins provide no benefits beyond the benefits already gained by eating the recommended daily allotment of fruits, vegetables, and whole grains.

Those who take multivitamins at least once a week take them, on average, 3.5 times a week.

Most people who take multivitamins at least once a week are also getting sufficient exercise.

Multivitamins provide no benefits beyond the benefits already gained by eating the recommended daily allotment of fruits, vegetables, and whole grains.

Explanation:

The article assumes, without stating, that multivitamins’ only benefits are equivalent to those gained by eating a proper amount of fruits, vegetables, and whole grains. If this assumption is false, the argument is invalid, as there could be other reasons to take multivitamins.

Example Question #12 : Necessary Assumption

Some recent classical music can be considered masterpieces. All masterpieces have a tight melodic structure. Furthermore, any piece of classical music that does not appeal to most aficionados of that musical genre cannot be deemed a masterpiece.

Each of the following statements follows logically from the assertions above EXCEPT:

Some classical music that appeals to aficionados of that genre have tight melodic structures.

Only classical music with a tight melodic structure and an appeal to aficionados of that genre can be deemed a masterpiece.

Only classical music that has a tight melodic structure appeals to classical music aficionados.

Some recent classical music have tight melodic structures.

Some recent classical music have tight melodic structure and appeal to aficionados of that genre.

Only classical music that has a tight melodic structure appeals to classical music aficionados.

Explanation:

This is a formal logic question that calls for an inference based upon the logical structure of the argument. It is best to reformulate the statements into simple conditional declarations (if-then statements) and then note the contrapositive. Here is a suggested reformulation: If masterpiece (M), then tight melodic structure (TMS). Contrapositive: If no TMS, then not M. If not appealing to aficionados (not A), then not M. Contrapositive: If M, then A. Some recent classical music (R) are masterpieces. Therefore, some R have TMS and are M. All of the answer choices that express one of these conditional statements follow logically from the argument presented. Those are the incorrect responses. The correct response—in effect, If TMS, then A (“Only classical music that has a tight melodic structure appeals to classical music aficionados”)—does not comport with any of these logical conditional statements.

Example Question #11 : Necessary Assumption

No Alphas are Xenons, but all Omegas are Xenons.  Therefore, no Omegas belong to the class of Homunculus.

Which one of the following assumptions permits the conclusion above to be properly drawn?

All members of the class of Homunculus are Alphas.

All members of the class of Homunculus are Xenons.

No Alphas are Omegas.

No members of the class of Homunculus are Alphas.

All Xenons are Omegas.

All members of the class of Homunculus are Alphas.

Explanation:

This is a formal logic problem.  First, note the conclusion:  If Omega, then not Homunculus.  Second, note the evidence/premises:  If Xenon, then not Alpha (or you can put it in its contrapositive form:  If Alpha, then not Xenon).; and If Omega, then Xenon.  To find the assumption, look for the missing term in the evidence/premises that does not appear in the conclusion---namely, Alpha.  So we can eliminate any answer choice that does not mention Alpha.

To elaborate in order to select the proper answer choice, we can see that the premises come down to this (combining the two propositions):  If Omega, then not Alpha.  The conclusion states:  If Omega, then not Homunculus.  Therefore, the assumption has to be If not Alpha, then not Homunculus.  Take the contrapositive of that:  If H, then A.  And that is what credited answer choice states.

Example Question #14 : Necessary Assumption

News programs that have public intellectuals as guests often result in high-level discussions about social issues that many find uncomfortable or disturbing.  For example, leftist intellectuals like Noam Chomsky and rightist intellectuals like William F. Buckley often angered and shocked television viewers, precisely because they prompted discussions that question basic assumptions many of us have about ourselves and the world.  It is therefore quite clear that news programs on PBS (Public Broadcasting System), because they do not shy away from having controversial public intellectuals as guests, should continue to receive public funding.

Which one of the following is an assumption that the above argument requires in order for its conclusion to be properly drawn?

Any discussion that disturbs or provokes discomfort is of a high level.

Chomsky and Buckley only appeared on programs that received public funding.

Programs on commercial television networks tend to be bland, or at least less likely to air controversial views that many could find disturbing or uncomfortable.

Public funding should be used to support the broadcasting of high-level discussions that many might find uncomfortable or disturbing.

Most high-level discussions of social issues are disturbing or provoke feelings of discomfort.

Public funding should be used to support the broadcasting of high-level discussions that many might find uncomfortable or disturbing.

Explanation:

The conclusion here is readily identifiable.  It advocates the use of PUBLIC FUNDS to support PBS news programs.  Why?  The answer to this "why?" question is our evidence:  the appearance of public intellectuals on news programs often lead to high-level discussions that many might find disturbing or controversial.  So the assumption needs to speak to the issue of "high-level discussions" that disturb many people since that is a term or idea that does not appear in the conclusion.  Moreover, that key term or idea must operate in a way to link the evidence to the key idea in the conclusion, which is the notion of "public funding."  The credited response does precisely that, whereas the wrong answer choices tend to go off in irrelevant or non-essential directions.

Example Question #15 : Necessary Assumption

A great film is not always appreciated by film critics when it is first released. In fact, many films now considered great were poorly reviewed upon their release; some critics even walked out of the initial screenings. Therefore, we must wait at least twenty years before determining the greatness of any particular film.

Which one of the following is an assumption that the argument requires in order for its conclusion to be properly drawn?

If a film is not appreciated twenty years after its release, it is not a great film.

If initial impressions of a film might be inaccurate, its greatness cannot be determined until a period of time has passed.

A film that is well-reviewed upon its release and remains appreciated after twenty years is unmistakably a great film.

Some film critics jump to conclusions when initially reviewing films which they later regret.

Most great films become more appreciated over time.

If initial impressions of a film might be inaccurate, its greatness cannot be determined until a period of time has passed.

Explanation:

Nothing in the argument as written explains why the greatness of a film cannot be determined upon its release. To draw that conclusion, the argument requires a connecting premise indicating that a period of time (in this case, twenty years) must elapse to determine greatness because initial impressions might be inaccurate. The other answer choices either restate premises already contained in the argument, or state premises which do not support the conclusion.

Example Question #16 : Necessary Assumption

Advertisement: Most cable companies are misleading you as to their prices. Their strategy is to advertise a low price, then tack on hidden fees after the customer has been “hooked.” The overall cost of that cable subscription often ends up to 20% higher than the advertised price. At Cool Cable, we state the full price of the subscription up front, so you know exactly what kind of deal you’re getting. This will help you make a more informed decision.

Which one of the following is an assumption on which the advertisement’s argument depends?

The advertised prices at Cool Cable are equal to or cheaper than other cable companies’ overall prices after taking into account the hidden fees.

Most people would prefer that the full price of a cable subscription is stated up front.

Most people are unaware of the hidden fees before ordering from other cable companies.

People will make less informed decisions if the full price of the product is not given until after they have been “hooked.”

People will make less informed decisions if the full price of the product is not given until after they have been “hooked.”

Explanation:

The argument states that giving the price up front will help people make a more informed decision than if they are charged hidden fees and given the total price later. For this statement to be valid, it must be true that decisions are less informed in the latter scenario. People’s awareness or preference as to the timing of prices are irrelevant; the key is whether they are more or less informed as a result of a particular advertising strategy.

Example Question #17 : Necessary Assumption

Some have argued that the Tibutu tribe know nothing about the concept of private property because the Tibutu do not have in their dialect any word or phrase that appears to capture the concept. But this is pure nonsense. A person who drinks water and uses it for bathing surely knows what water is, even if that person has no word for it.

Which one of the following is an assumption required by the argument?

One need not have a word or phrase for water before knowing what water is.

Those who experience something know it better than those who merely have a name for that something.

Naming something and knowing something need not be the same thing.

Naming something is useless in getting to know that something.

Knowing what something is necessarily involves attaching a word or phrase to that something.

One need not have a word or phrase for water before knowing what water is.

Explanation:

First we must identify the conclusion: It is wrong to conclude that the Tibutu do not understand the concept of private property. Second we must articulate the premise or evidence for that conclusion: drinking and using water can lead to knowledge of water, even without attaching a name to it (experiencing something is enough to gain knowledge of that thing). The assumption must link the premise or evidence to the conclusion. To do that, we must identify the word, phrase, or concept (or idea) in the premise or evidence that does not appear in the conclusion. That is relatively easy here—the idea of experiencing water as a way to gain knowledge of it is the key point that must appear in the assumption. The correct response expresses the key idea in the premise and links it to the conclusion. Note that the answer choice that invokes the idea of experiencing something as a way to know it states something extreme—namely, that is “better” to experience something than to have a name for it when it comes to gaining knowledge of it. While perhaps true, that qualitative judgment is not expressed or implied in the argument, so it is not the correct answer choice.

Example Question #18 : Necessary Assumption

Spiritual guru: All forms of analysis involve making distinctions, which is nothing more than using logic like a knife to slice up so-called “Reality". So we can say that analytical thought necessarily ignores the unifying features of all material forms and concepts. It likewise follows that non-analytical thought that embraces spiritual sensibilities is a more profound form of engagement with reality.

Which one of the following is an assumption necessary for the spiritual guru’s conclusion to be properly drawn?

Spiritual enlightenment entails grasping the unity of all material forms and concepts.

Grasping the unity of material forms and concepts constitutes a more profound way to engage with “reality” than using analysis to understand “reality.”

Those who have strong analytical abilities can never gain spiritual enlightenment.

It is impossible to grasp the unity of material forms and concepts if one engages in analytical thought to understand how something works.

Making distinctions through analytical thought clouds one’s perception of “reality.”

Grasping the unity of material forms and concepts constitutes a more profound way to engage with “reality” than using analysis to understand “reality.”

Explanation:

To derive the assumption, we must first identify the conclusion of the argument—to wit, “Non-analytical thought offers a more profound way to engage with reality than does analytical thought.” What is the evidence or premise to that conclusion? We can express it as something like this, as a paraphrase of what is expressed fully in the argument: “Analytical thought ignores ‘unity’ of all things.” What is a term or concept in the premise that does not appear in the conclusion? Answer: the notion of “unity.” So the assumption must contain within it some expression of that notion. More particularly, the assumption involves some notion of “grasping unity” as a way to penetrate “reality” in a more profound way. The credited answer choice expresses that notion precisely. The others miss the mark inasmuch as they do not express the key idea of “grasping unity” as a way to understand “reality” in a “profound” way.

Example Question #19 : Necessary Assumption

Psychologist: Those suffering addictions to alcohol or drugs often rely on people close to them to facilitate their maladaptive behavior. They often manipulate others to feel guilty by withdrawing affection or attention until the other person capitulates and seeks to ingratiate him or herself to the addict. The person then caters to the addict, helps the addict get what he or she wants—namely, drink or drugs—and their relationship has some semblance of being strengthened. This pattern of guilt-inducement and guilt-relieving behavior by the addict and the facilitating partner is repeated such that the level of manipulation escalates to the point of intolerability.

The description offered by the psychologist best illustrates which one of the following generalizations?

An addict and a significant other can mutually influence each other’s behavior.

All addicts are manipulative and should therefore not be trusted.

The best way to help an addict is to sever all intimate ties with him or her.

Inducing guilt in others is a learned behavior that goes in tandem with drug or alcohol abuse.

Addicts are incapable of having quality intimate relationships, so long as they continue to abuse drugs or alcohol.

An addict and a significant other can mutually influence each other’s behavior.

Explanation:

The psychologist gives a description of a certain repeated pattern of behavior which involves an addict and another person to whom the addict is close. That pattern reflects how one person’s behavior triggers responding behavior by the other, such that the behavior of both people is constantly being reinforced. The credited response must capture this mutual-reinforcement phenomenon. The argument by the psychologist is not calculated to tag all addicts as manipulative and untrustworthy; nor does it warn against having an intimate relationship with all addicts. Finally, the argument does not concern itself with how an addict develops his or her behavior pattern. So all of the other answer choices, to one degree or another, miss the mark.

Example Question #20 : Necessary Assumption

Political scientist:  Quality public education at the high school level leads to a citizenry more attuned to the problems of the community and of the society at large.  But quality public education at the high school level does not necessarily lead to a citizenry capable of discerning which politicians are best equipped to address those problems, since campaign money can distort how arguments for change are presented.  Consequently, rapid but foolhardy change may occur in a society that quickly improves its public education system at the high school level but does not address the problem of money in politics.

Which one of the following is an assumption on which the political scientist's argument depends?

All societes that fail to control the flow of money in politics will be undermined by the poor decisionmaking of the citizenry.

Without a quality public school system at the high school level, there can be no genuine social reform.

Unbridled campaign contributions to candidates affect the ability of citizens to differentiate which politicians are better equipped to address community and social problems.

Campaign reforms designed to control the flow of money in politics will likely lead to a pace of social change that is appropriate to the society.

A politician who receives large campaign contributions ought not to be supported by the citizenry.

Unbridled campaign contributions to candidates affect the ability of citizens to differentiate which politicians are better equipped to address community and social problems.

Explanation:

First, identify the conclusion:  "Rapid but foolhardy change may occur in a society that quickly improves its public education system at the high school level but does not address the problem of money in politics."

Second, identify the key terms in the evidence/premises with a paraphrase of what is presented in the passage:  for example, you might say, "campaign contributions (money in politics) distorts the electoral process."

What key term in the evidence/premises does not appear in the conclusion? Obviously, something relating to unbridled campaign contributions (i.e., the distorting affects of money in politics).  That key term or idea must be at work in the assumption, and therefore it must appear in the correct answer choice.  So we can quickly eliminate any answer choice that does not speak to this key term or idea.

The credited response speaks directly to the distorting effects of uncontrolled money in politics without the use of extreme language and without resort to unnecessary "ought" or "should" assertions.  Note how the wrong answers either use extreme language or resort to claims that urge some kind of action (whereas the argument does not assume something about action that is needed---though it may lead to an INFERENCE that certain action would be wise, but that is not an assumption).

Tired of practice problems?

Try live online LSAT prep today.