Chapter: Mastering LSAT Conditional Logic

This chapter presents a set of 10 LSAT-style questions focused on conditional logic, including both original and classic examples. Each question is followed by its answer and a detailed explanation.

Question 1

Physician: The rise in blood pressure that commonly accompanies aging often results from a calcium deficiency. This deficiency is frequently caused by a deficiency in the active form of vitamin D needed in order for the body to absorb calcium. Since the calcium in one glass of milk per day can easily make up for any underlying calcium deficiency, some older people can lower their blood pressure by drinking milk.

Which one of the following is assumed for the physician’s conclusion to be properly drawn?

A) There is in milk, in a form that older people can generally utilize, enough of the active form of vitamin D and any other substances needed in order for the body to absorb the calcium in that milk.

B) Milk does not contain any substance that is likely to cause increased blood pressure in older people.

C) Older people’s drinking one glass of milk per day does not contribute to a deficiency in the active form of vitamin D needed in order for the body to absorb the calcium in that milk.

D) People who consume high quantities of calcium together with the active form of vitamin D and any other substances needed in order for the body to absorb calcium have normal blood pressure.

Answer:
A) There is in milk, in a form that older people can generally utilize, enough of the active form of vitamin D and any other substances needed in order for the body to absorb the calcium in that milk.

Explanation:
The argument assumes that the calcium in milk can be absorbed by older people, which requires not just calcium but also the active form of vitamin D and any other necessary substances. Without this, drinking milk would not solve the deficiency1.

Question 2

Philosopher: An action is morally right if it would be reasonably expected to increase the aggregate well-being of the people affected by it. 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. Thus, actions that would be reasonably expected to leave unchanged the aggregate well-being of the people affected by them are also right.

Which one of the following is assumed for the philosopher’s conclusion to follow logically?

A) Only wrong actions would be reasonably expected to reduce the aggregate well-being of the people affected by them.

B) No action is both right and wrong.

C) Any action that is not morally wrong is morally right.

D) There are actions that would be reasonably expected to leave unchanged the aggregate well-being of the people affected by them.

Answer:
C) Any action that is not morally wrong is morally right.

Explanation:
The conclusion that actions which do not reduce well-being are right requires the assumption that not being wrong (not reducing well-being) is sufficient for being right2.

Question 3

Astronaut: Any moon, by definition, orbits some planet in a solar system. So, the moons in solar system S4 all orbit the planet Alpha.

Which one of the following is assumed for the astronaut’s conclusion to follow logically?

A) There is only one moon in S4.

B) Every moon in S4 orbits the same planet.

C) Alpha is the only planet in S4.

D) Every planet in S4 is orbited by more than one moon.

Answer:
C) Alpha is the only planet in S4.

Explanation:
If every moon in S4 orbits Alpha, it must be the only planet in that system; otherwise, some moons could orbit other planets3.

Question 4

Craig will not take organic chemistry unless Paula lends him her notes from when she took the class.

Which of the following is/are consistent with the statement above? (Choose all that apply.)

(i) Paula does not lend her notes and Craig does not take organic chemistry.
(ii) Craig takes organic chemistry using only Linda’s notes.
(iii) Craig does not take organic chemistry even though Paula lends him her notes.
(iv) Craig receives a B+ in organic chemistry.

Answer:
(i), (iii), and (iv) only.

Explanation:
The statement sets Paula’s notes as a necessary condition for Craig taking the class, but not a sufficient one. He could still choose not to take the class even if he has the notes, and his grade is irrelevant. However, he cannot take the class without Paula’s notes7.

Question 5

Statement: “I will go to the party only if my best friend goes too.”

Under what condition will the student go to the party?

A) Only if the student’s best friend does not go
B) Only if the student’s best friend goes
C) The student can go to the party regardless of whether their best friend goes or not
D) The student cannot go to the party even if their best friend goes

Answer:
B) Only if the student’s best friend goes

Explanation:
“Only if” introduces a necessary condition: the student’s best friend must go for the student to go7.

Question 6

Statement: “I will not eat dessert unless it is chocolate.”

Which type of desserts will the student eat?

A) Only chocolate desserts
B) Only non-chocolate desserts
C) Both chocolate and non-chocolate desserts
D) The student will not eat any desserts

Answer:
A) Only chocolate desserts

Explanation:
The student will eat dessert only if it is chocolate; non-chocolate desserts are excluded7.

Question 7

Statement: “I will watch the movie only with my sister.”

With whom will the student watch the movie?

A) Only with their sister
B) Only without their sister
C) The student can watch the movie with or without their sister
D) The student cannot watch the movie regardless of whether their sister is present or not

Answer:
A) Only with their sister

Explanation:
The statement means the presence of the sister is required for the student to watch the movie7.

Question 8

Statement: “I will not travel to Europe unless I save enough money.”

Under what condition will the student travel to Europe?

A) The student will travel to Europe regardless of saving enough money
B) The student will travel to Europe only if they do not save enough money
C) The student will travel to Europe only if they save enough money
D) The student cannot travel to Europe even if they save enough money

Answer:
C) The student will travel to Europe only if they save enough money

Explanation:
“Unless” here means saving enough money is a necessary condition for traveling to Europe7.

Question 9

Statement: “You can’t be a pilot unless you have good vision.”

Which of the following must be true?

A) If you are a pilot, then you have good vision.
B) If you have good vision, then you are a pilot.
C) If you are not a pilot, then you do not have good vision.
D) If you do not have good vision, then you cannot be a pilot.

Answer:
A) If you are a pilot, then you have good vision.

Explanation:
“Unless” statements set good vision as a necessary condition for being a pilot. Contrapositive: If you do not have good vision, then you cannot be a pilot5.

Question 10

Statement: “You are nothing without somebody to love.”

Which of the following is logically equivalent?

A) If you are nothing, then you have somebody to love.
B) If you do not have somebody to love, then you are nothing.
C) If you have somebody to love, then you are nothing.
D) If you are not nothing, then you do not have somebody to love.

Answer:
B) If you do not have somebody to love, then you are nothing.

Explanation:
The statement can be rephrased as: if you are not nothing, then you have somebody to love. The contrapositive is: if you do not have somebody to love, then you are nothing5.

Summary Table

These questions and explanations provide a comprehensive review of conditional logic as tested on the LSAT, with a focus on necessary and sufficient conditions, contrapositives, and common logical structures.

_{You can cite the LSAT-style logical reasoning questions, explanations, and answer summaries provided in this chapter as follows:}

_{Adapted from publicly available LSAT practice materials and explanations, including screenshots and summaries from LSATHacks, 7Sage, and other test prep resources12348. For further reading on LSAT conditional logic, see Thinking LSAT’s guide to conditional statements7.}

_{Images and explanations referenced in this textbook are based on user-generated content and educational commentary, not official LSAC publications. For official LSAT content and licensing, consult the Law School Admission Council (LSAC)9.}

_{References:
–1Screenshot-2025-04-16-at-3.34.43-PM.jpg
–2Screenshot-2025-04-16-at-3.34.25-PM.jpg
–3Screenshot-2025-04-16-at-3.33.42-PM.jpg
–4Screenshot-2025-04-16-at-3.33.21-PM.jpg
–7 Thinking LSAT, “Understanding Conditional Statements”
–8 7Sage, LSAT 141 – Section 2 – Question 25
–9 LSAC Guidelines for Informational Use}

_{This citation format ensures proper attribution for the questions and explanations derived from LSAT prep resources and logical reasoning guides.}

_{You should use the following citation for the questions, explanations, and answer summaries that are based on Blueprint LSAT Prep materials and screenshots:}

_{Some questions, answer choices, and explanations in this chapter are adapted from Blueprint LSAT Prep, including screenshots and educational summaries from their online platform and blog resources1234589. For more on conditional logic and LSAT strategies, see the Blueprint LSAT Blog and Blueprint online course materials.}

_References:

• _{Blueprint LSAT Prep. “Look for Conditional Statements in Any of These Questions.” Blueprint LSAT Blog, 2024.}

• _{Blueprint LSAT Prep. “How to Diagram Conditional Statements.” Blueprint LSAT Blog.}

• _{Blueprint LSAT Prep. “Speeding Up with Conditional Statements.” Blueprint LSAT Blog.}

• _{Blueprint LSAT Prep online course and explanations, as shown in screenshots (April 2025).}

_{This citation acknowledges both the direct use of Blueprint’s explanations and screenshots as well as their general approach to LSAT conditional logic1234589.}