We typically use the term “new” or “rogue” to refer to an element that appears only in
the conclusion or only in a premise.
If you see a weakness in the argument, look for an answer that eliminates the weakness
or assumes that it does not exist. In other words, close the gaps in the argument.
Supporter answer choices lend themselves well to prephrasing. Defender answers do not
because there are too many possibilities to choose from.
Most LSAT publications and courses present a limited description of
assumptions. An assumption is described solely as a linking statement, one that
links two premises or links a premise to the conclusion. If no other description
of assumptions is given, this limited presentation cheats students of the
possibility of fully understanding the way assumptions work within arguments
and the way they are tested by the makers of the exam.
On the LSAT, assumptions play one of two roles—the Supporter or the
Defender. The Supporter role is the traditional linking role, where an
assumption connects the pieces of the argument. Consider the following
example:
All male citizens of Athens had the right to vote. Therefore, Socrates
had the right to vote in Athens.
The linking assumption is that Socrates was a male citizen of Athens. This
connects the premise element of male citizens having the right to vote and the
conclusion element that Socrates had the right to vote (affiliated assumptions are
“Socrates was male” and “Socrates was a citizen of Athens”).
Because Supporters often connect “new” or “rogue” pieces of information in
the argument, the Supporter role generally appears similar to the Justify the
Conclusion answers discussed in the previous section. In fact, a number of
correct Justify the Conclusion answers are assumptions of the argument,
especially when the argument contains a conditional structure. This is actually a
benefit because if you mis-identify a Justify question as an Assumption question
there is still a reasonable possibility that you can answer the question correctly.
Supporter assumptions on the LSAT are often relatively easy for students to
identify because they can see the gap in the argument. The Supporter
assumption, by definition, closes the hole by linking the elements together.
Should you ever see a gap or a new element in the conclusion, a Supporter
assumption answer will almost certainly close the gap or link the new element
back to the premises.
The Defender role is entirely different, and Defender assumptions protect the
argument by eliminating ideas that could weaken the argument. Consider our
discussion from Chapter Two:
“When you read an LSAT argument from the perspective of the author,
keep in mind that he or she believes that their argument is sound. In
other words, they do not knowingly make errors of reasoning. This is a
fascinating point because it means that LSAT authors, as part of the
LSAT world, function as if the points they raise and the conclusions
they make have been well-considered and are airtight.”
By assuming that any threat to the argument does not exist, the author can present the
argument and claim it is valid. If the author knew of imperfections and still presented the
argument without a caveat, then the author would be hard-pressed to claim that this
conclusion— especially an absolute one— was reasonable.
This fundamental truth of the LSAT has a dramatic impact when you consider
the range of assumptions that must be made by an LSAT author. In order to
believe the argument is “well-considered and airtight,” an author must assume
that every possible objection has been considered and rejected. Consider the
following causal argument:
People who read a lot are more intelligent than other people. Thus,
reading must cause a person to be intelligent.
Although the conclusion is questionable (for example, the situation may be
reversed: intelligence might be the cause of reading a lot), in the author’s mind
all other alternative explanations are assumed not to exist. Literally, the author
assumes that any idea that would weaken the argument is impossible and cannot
occur. Consider some of the statements that would attack the conclusion above:
Sleeping more than eight hours causes a person to be intelligent.
Regular exercise causes a person to be intelligent.
A high-protein diet causes a person to be intelligent.
Genetics cause a person to be intelligent.
Each of these ideas would undermine the conclusion, but they are assumed by
the author not to be possible, and the author therefore makes the following
assumptions in the original argument:
Sleeping more than eight hours does not cause a person to be intelligent.
Regular exercise does not cause a person to be intelligent.
A high-protein diet does not cause a person to be intelligent.
Genetics do not cause a person to be intelligent.
These assumptions protect the argument against statements that would
undermine the conclusion. In this sense, they “defend” the argument by
showing that a possible avenue of attack has been eliminated (assumed not to
exist). As you can see, this list could go on and on because the author assumes
every alternate cause does not exist. This means that although the argument only
discussed reading and intelligence, we suddenly find ourselves with
assumptions addressing a wide variety of topics that were never discussed in the
stimulus. In a typical argument, there are an infinite number of assumptions
possible, with most of those coming on the Defender side. Books and courses
that focus solely on the Supporter role miss these assumptions, and students
who do not understand how Defenders work will often summarily dismiss
answer choices that later prove to be correct.
Let’s review the two roles played by assumptions:
Supporter Assumption: These assumptions link together new or rogue
elements in the stimulus or fill logical gaps in the
argument.
Defender Assumption: These assumptions contain statements that
eliminate ideas or assertions that would
undermine the conclusion. In this sense, they
“defend” the argument by showing that a
possible source of attack has been eliminated.
Let us examine examples of each type. Please take a moment to complete the
following question:
1. Art historian: Great works of art have often elicited
outrage when first presented; in Europe,
Stravinsky’s Rite of Spring prompted a riot, and
Manet’s Déjeuner sur l’herbe elicited outrage
and derision. So, since it is clear that art is often
shocking, we should not hesitate to use public
funds to support works of art that many people
find shocking.
Which one of the following is an assumption that the
art historian’s argument requires in order for its
conclusion to be properly drawn?
(A) Most art is shocking.
(B) Stravinsky and Manet received public funding
for their art.
(C) Art used to be more shocking than it currently
is.
(D) Public funds should support art.
(E) Anything that shocks is art.
Once you understand the way Supporters work, they can often be predicted after
you read an argument.
This is a very challenging Supporter assumption, and only about half of the test
takers identify the correct answer. Take a close look at the conclusion: “we
should not hesitate to use public funds to support works of art that many people
find shocking.” Did “public funds” appear anywhere else in the argument? No.
Given our discussion about linking new elements that appear in the conclusion,
you should have recognized that a new element was present and responded
accordingly. Given that Supporters connect new elements, one would suspect
that the correct answer would include this element and that either answer choice
(B) or (D) was correct. Take a look at the argument structure:
Premise: Great works of art have often elicited outrage when first
presented; in Europe, Stravinsky’s Rite of Spring prompted a
riot, and Manet’s Déjeuner sur l’herbe elicited outrage and
derision.
Premise: Art is often shocking.
Conclusion: We should not hesitate to use public funds to support works
of art that many people find shocking.
However, because the structure of the last sentence in the stimulus (“So,
since...”) suggests that the author uses the second premise to prove the
conclusion, you should focus on the relationship between those two pieces. For
the author to say that art is shocking and therefore art should be publicly
funded, the author must assume that art is worthy of public support. This
assumption is reflected in answer choice (D), the correct answer.
Answer choice (A): The author states that “art is often shocking” but does not
assume that most art is shocking.
Answer choice (B): This is the most popular wrong answer choice. In the
argument, is the author committed to believing that Stravinsky and Manet
received public funding? Does the author need this statement in order for the
rest of the argument to work? No. The author uses Stravinsky and Manet as
examples of artists whose work caused shock, but the author never assumes that
those individuals received public funding. Think for a moment—does the
conclusion rest on the fact that Stravinsky and Manet received public funding?
Answer choice (C): The author makes no statement regarding the “shock level”
of today’s art, and thus there is no way to determine if an assumption has been
made comparing the shock level of past and present art.
Answer choice (D): This is the correct answer. The answer acts as a Supporter
and connects the elements in the final sentence.
Answer choice (E): The author states that “art is often shocking,” but there is no
indication that a conditional assumption has been made stating that anything that
shocks is art.
Now let us look at a Defender assumption. Please take a moment to complete
the following question:
2. In Western economies, more energy is used to operate
buildings than to operate transportation. Much of the
decline in energy consumption since the oil crisis of
1973 is due to more efficient use of energy in homes
and offices. New building technologies, which make
lighting, heating, and ventilation systems more
efficient, have cut billions of dollars from energy
bills in the West. Since energy savings from these
efficiencies save several billion dollars per year
today, we can conclude that 50 to 100 years from
now they will save more than $200 billion per year
(calculated in current dollars).
On which one of the following assumptions does the
argument rely?
(A) Technology used to make buildings energy
efficient will not become prohibitively
expensive over the next century.
(B) Another oil crisis will occur in the next 50 to
100 years.
(C) Buildings will gradually become a less
important consumer of energy than
transportation.
(D) Energy bills in the West will be $200 billion
lower in the next 50 to 100 years.
(E) Energy-efficient technologies based on new
scientific principles will be introduced in the
next 50 to 100 years.
Unlike Supporter assumptions, Defender assumptions are extremely hard to
prephrase because there are so many possibilities for the test makers to choose
from. The correct answer in this problem is a Defender, but it is unlikely that
anyone could have predicted the answer. Compare this to the previous problem,
where many students were able to prephrase the correct Supporter answer.
Now, focus on the final sentence of the argument, which contains a premise and
conclusion:
Premise: Energy savings from these efficiencies [new building
technologies] save several billion dollars per year today.
Conclusion: 50 to 100 years from now they will save more than $200
billion per year (calculated in current dollars).
So, according to the author, the new building technologies—which are already
saving billions—will continue to do the same in the future and the savings will
be even greater, relatively.
Answer choice (A): This is the correct answer, and a classic Defender. If the
money-saving and energy-saving technology becomes too expensive to use in
the next 100 years, the savings expected will not materialize. Because this idea
would clearly weaken the argument, the author assumes that it does not exist,
and answer choice (A) denies that the technology will become prohibitively
expensive over the next century.
Answer choice (B): Although there has been an energy usage decline since the
1973 oil crisis, the author does not assume that there will be another crisis in the
next 50 to 100 years. Look at the conclusion—does there seem to be a reliance
on the idea in this answer? No.
Answer choice (C): Although this answer plays with the idea mentioned in the
first sentence of the stimulus—that more energy is used to operate buildings
than to operate transportation—no assumption is made that buildings will
become a less important consumer of energy. True, buildings have saved
billions in operating in costs, but the conclusion is about future savings and not
about comparing buildings to transportation.
Answer choice (D): The argument is specific about technologies saving more
than $200 billion per year; the author does not assume that the total bill in the
next 50 to 100 years will be lower by $200 billion.
Answer choice (E): The argument is about current technologies saving money
in the future. The author does not make an assumption regarding new
technologies being introduced in the future.
the conclusion or only in a premise.
If you see a weakness in the argument, look for an answer that eliminates the weakness
or assumes that it does not exist. In other words, close the gaps in the argument.
Supporter answer choices lend themselves well to prephrasing. Defender answers do not
because there are too many possibilities to choose from.
Most LSAT publications and courses present a limited description of
assumptions. An assumption is described solely as a linking statement, one that
links two premises or links a premise to the conclusion. If no other description
of assumptions is given, this limited presentation cheats students of the
possibility of fully understanding the way assumptions work within arguments
and the way they are tested by the makers of the exam.
On the LSAT, assumptions play one of two roles—the Supporter or the
Defender. The Supporter role is the traditional linking role, where an
assumption connects the pieces of the argument. Consider the following
example:
All male citizens of Athens had the right to vote. Therefore, Socrates
had the right to vote in Athens.
The linking assumption is that Socrates was a male citizen of Athens. This
connects the premise element of male citizens having the right to vote and the
conclusion element that Socrates had the right to vote (affiliated assumptions are
“Socrates was male” and “Socrates was a citizen of Athens”).
Because Supporters often connect “new” or “rogue” pieces of information in
the argument, the Supporter role generally appears similar to the Justify the
Conclusion answers discussed in the previous section. In fact, a number of
correct Justify the Conclusion answers are assumptions of the argument,
especially when the argument contains a conditional structure. This is actually a
benefit because if you mis-identify a Justify question as an Assumption question
there is still a reasonable possibility that you can answer the question correctly.
Supporter assumptions on the LSAT are often relatively easy for students to
identify because they can see the gap in the argument. The Supporter
assumption, by definition, closes the hole by linking the elements together.
Should you ever see a gap or a new element in the conclusion, a Supporter
assumption answer will almost certainly close the gap or link the new element
back to the premises.
The Defender role is entirely different, and Defender assumptions protect the
argument by eliminating ideas that could weaken the argument. Consider our
discussion from Chapter Two:
“When you read an LSAT argument from the perspective of the author,
keep in mind that he or she believes that their argument is sound. In
other words, they do not knowingly make errors of reasoning. This is a
fascinating point because it means that LSAT authors, as part of the
LSAT world, function as if the points they raise and the conclusions
they make have been well-considered and are airtight.”
By assuming that any threat to the argument does not exist, the author can present the
argument and claim it is valid. If the author knew of imperfections and still presented the
argument without a caveat, then the author would be hard-pressed to claim that this
conclusion— especially an absolute one— was reasonable.
This fundamental truth of the LSAT has a dramatic impact when you consider
the range of assumptions that must be made by an LSAT author. In order to
believe the argument is “well-considered and airtight,” an author must assume
that every possible objection has been considered and rejected. Consider the
following causal argument:
People who read a lot are more intelligent than other people. Thus,
reading must cause a person to be intelligent.
Although the conclusion is questionable (for example, the situation may be
reversed: intelligence might be the cause of reading a lot), in the author’s mind
all other alternative explanations are assumed not to exist. Literally, the author
assumes that any idea that would weaken the argument is impossible and cannot
occur. Consider some of the statements that would attack the conclusion above:
Sleeping more than eight hours causes a person to be intelligent.
Regular exercise causes a person to be intelligent.
A high-protein diet causes a person to be intelligent.
Genetics cause a person to be intelligent.
Each of these ideas would undermine the conclusion, but they are assumed by
the author not to be possible, and the author therefore makes the following
assumptions in the original argument:
Sleeping more than eight hours does not cause a person to be intelligent.
Regular exercise does not cause a person to be intelligent.
A high-protein diet does not cause a person to be intelligent.
Genetics do not cause a person to be intelligent.
These assumptions protect the argument against statements that would
undermine the conclusion. In this sense, they “defend” the argument by
showing that a possible avenue of attack has been eliminated (assumed not to
exist). As you can see, this list could go on and on because the author assumes
every alternate cause does not exist. This means that although the argument only
discussed reading and intelligence, we suddenly find ourselves with
assumptions addressing a wide variety of topics that were never discussed in the
stimulus. In a typical argument, there are an infinite number of assumptions
possible, with most of those coming on the Defender side. Books and courses
that focus solely on the Supporter role miss these assumptions, and students
who do not understand how Defenders work will often summarily dismiss
answer choices that later prove to be correct.
Let’s review the two roles played by assumptions:
Supporter Assumption: These assumptions link together new or rogue
elements in the stimulus or fill logical gaps in the
argument.
Defender Assumption: These assumptions contain statements that
eliminate ideas or assertions that would
undermine the conclusion. In this sense, they
“defend” the argument by showing that a
possible source of attack has been eliminated.
Let us examine examples of each type. Please take a moment to complete the
following question:
1. Art historian: Great works of art have often elicited
outrage when first presented; in Europe,
Stravinsky’s Rite of Spring prompted a riot, and
Manet’s Déjeuner sur l’herbe elicited outrage
and derision. So, since it is clear that art is often
shocking, we should not hesitate to use public
funds to support works of art that many people
find shocking.
Which one of the following is an assumption that the
art historian’s argument requires in order for its
conclusion to be properly drawn?
(A) Most art is shocking.
(B) Stravinsky and Manet received public funding
for their art.
(C) Art used to be more shocking than it currently
is.
(D) Public funds should support art.
(E) Anything that shocks is art.
Once you understand the way Supporters work, they can often be predicted after
you read an argument.
This is a very challenging Supporter assumption, and only about half of the test
takers identify the correct answer. Take a close look at the conclusion: “we
should not hesitate to use public funds to support works of art that many people
find shocking.” Did “public funds” appear anywhere else in the argument? No.
Given our discussion about linking new elements that appear in the conclusion,
you should have recognized that a new element was present and responded
accordingly. Given that Supporters connect new elements, one would suspect
that the correct answer would include this element and that either answer choice
(B) or (D) was correct. Take a look at the argument structure:
Premise: Great works of art have often elicited outrage when first
presented; in Europe, Stravinsky’s Rite of Spring prompted a
riot, and Manet’s Déjeuner sur l’herbe elicited outrage and
derision.
Premise: Art is often shocking.
Conclusion: We should not hesitate to use public funds to support works
of art that many people find shocking.
However, because the structure of the last sentence in the stimulus (“So,
since...”) suggests that the author uses the second premise to prove the
conclusion, you should focus on the relationship between those two pieces. For
the author to say that art is shocking and therefore art should be publicly
funded, the author must assume that art is worthy of public support. This
assumption is reflected in answer choice (D), the correct answer.
Answer choice (A): The author states that “art is often shocking” but does not
assume that most art is shocking.
Answer choice (B): This is the most popular wrong answer choice. In the
argument, is the author committed to believing that Stravinsky and Manet
received public funding? Does the author need this statement in order for the
rest of the argument to work? No. The author uses Stravinsky and Manet as
examples of artists whose work caused shock, but the author never assumes that
those individuals received public funding. Think for a moment—does the
conclusion rest on the fact that Stravinsky and Manet received public funding?
Answer choice (C): The author makes no statement regarding the “shock level”
of today’s art, and thus there is no way to determine if an assumption has been
made comparing the shock level of past and present art.
Answer choice (D): This is the correct answer. The answer acts as a Supporter
and connects the elements in the final sentence.
Answer choice (E): The author states that “art is often shocking,” but there is no
indication that a conditional assumption has been made stating that anything that
shocks is art.
Now let us look at a Defender assumption. Please take a moment to complete
the following question:
2. In Western economies, more energy is used to operate
buildings than to operate transportation. Much of the
decline in energy consumption since the oil crisis of
1973 is due to more efficient use of energy in homes
and offices. New building technologies, which make
lighting, heating, and ventilation systems more
efficient, have cut billions of dollars from energy
bills in the West. Since energy savings from these
efficiencies save several billion dollars per year
today, we can conclude that 50 to 100 years from
now they will save more than $200 billion per year
(calculated in current dollars).
On which one of the following assumptions does the
argument rely?
(A) Technology used to make buildings energy
efficient will not become prohibitively
expensive over the next century.
(B) Another oil crisis will occur in the next 50 to
100 years.
(C) Buildings will gradually become a less
important consumer of energy than
transportation.
(D) Energy bills in the West will be $200 billion
lower in the next 50 to 100 years.
(E) Energy-efficient technologies based on new
scientific principles will be introduced in the
next 50 to 100 years.
Unlike Supporter assumptions, Defender assumptions are extremely hard to
prephrase because there are so many possibilities for the test makers to choose
from. The correct answer in this problem is a Defender, but it is unlikely that
anyone could have predicted the answer. Compare this to the previous problem,
where many students were able to prephrase the correct Supporter answer.
Now, focus on the final sentence of the argument, which contains a premise and
conclusion:
Premise: Energy savings from these efficiencies [new building
technologies] save several billion dollars per year today.
Conclusion: 50 to 100 years from now they will save more than $200
billion per year (calculated in current dollars).
So, according to the author, the new building technologies—which are already
saving billions—will continue to do the same in the future and the savings will
be even greater, relatively.
Answer choice (A): This is the correct answer, and a classic Defender. If the
money-saving and energy-saving technology becomes too expensive to use in
the next 100 years, the savings expected will not materialize. Because this idea
would clearly weaken the argument, the author assumes that it does not exist,
and answer choice (A) denies that the technology will become prohibitively
expensive over the next century.
Answer choice (B): Although there has been an energy usage decline since the
1973 oil crisis, the author does not assume that there will be another crisis in the
next 50 to 100 years. Look at the conclusion—does there seem to be a reliance
on the idea in this answer? No.
Answer choice (C): Although this answer plays with the idea mentioned in the
first sentence of the stimulus—that more energy is used to operate buildings
than to operate transportation—no assumption is made that buildings will
become a less important consumer of energy. True, buildings have saved
billions in operating in costs, but the conclusion is about future savings and not
about comparing buildings to transportation.
Answer choice (D): The argument is specific about technologies saving more
than $200 billion per year; the author does not assume that the total bill in the
next 50 to 100 years will be lower by $200 billion.
Answer choice (E): The argument is about current technologies saving money
in the future. The author does not make an assumption regarding new
technologies being introduced in the future.
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