The most basic logic rule is the Conditional (which is just a phrase like A → B). We can diagram conditionals by abbreviating them and then using an arrow (→) to join the statements.

1. Followers:

If A, then B.

If James competes, then Macro must go to the race as a coach.

1. SUFFICIENT CONDITIONS

Now were going to delve into the specifics of how to identify necessary and sufficient conditions on the LSAT and then diagram them.

Sufficient Conditions Video Summary

  • 0:23 – The sufficient condition is the one on the left side of a conditional statement (if-then relationship).
  • 0:53 – There are terms we can look for to recognize whether a condition is a sufficient one or a necessary one. We call these as language cues or “indicator words”.
  • 2:07 – The sufficient indicators help you determine a sufficient condition. These keywords are listed on the LSAT Sufficient Indicators sub-section.
  • 2:24 – For example: The dog barks every time someone knocks on the door. The sufficient indicator keyword “every” helps us determine the sufficient condition “. . . someone knocks on the door”.
  • 2:52 – We can then diagram the statement where “. . . someone knocks on the door.” (K) is on the left side of the conditional while “The dog barks . . .” (B) is on the right side. The diagram becomes: K → B.
  • 2:58 – As another example, consider the statement: Whoever is kind is loved. The keyword “whoever” tells us that the sufficient condition is the phrase “. . . is kind . . .”, so the necessary condition is the phrase “. . . is loved.”.
  • 3:44 – We can then diagram this statement as follows: K → L.
  • 4:02 – As another example, consider the statement: Flowers were the only decorations. The indicator “the only” tells us that “. . . decorations.” (D) is the sufficient condition, while “ . .” (F) is the necessary condition.
  • 4:25 – We can then express this as: D → F.

LSAT Sufficient Indicators: these are keywords that indicate a sufficient condition.

  • If
  • If only
  • All
  • Any
  • Each
  • Every
  • When
  • Whenever
  • Whoever
  • Whatever
  • Whenever
  • People who
  • In order
  • Any

1a. Diagram Sufficient Conditionals

Sufficient indicator phrases like if… then or when are straightforward to diagram. They use the basic structure:
sufficient indicator [sufficient] → [necessary]

Diagram: When your cell phone rings in a theater, people will glare at you.

1. Locate the sufficient indicator (helping tell you that it is a sufficient conditional):

When your cell phone rings in a theater, people will glare at you.

2. Locate the [conditional phrase] after the sufficient indicator: When [your cell phone rings in a theater]…. (that phrase is the sufficient conditionthe first part).

3. Abbreviate it: PRT (phone rings theater)

4. Locate the necessary “result” in the conditional:  …[people will glare at you] (that’s the necessary conditionthe second part).

5. Abbreviate it: PGY (people glare you)

6. Put abbreviations into a sufficientnecessary diagram: PRTPGY

Next LSAT: October 28th

1b. Sufficient: Each, If, Every, Any

If every member of a group has a trait, then you can just do (group [sufficient]) (trait [necessary]).

All A’s are B’s is the same thing as A → B.

All dogs are mammals

Solution

  1. Locate the sufficient indicator: All
  2. Locate the conditional phrase right after the sufficient indicator: “. . . dogs . . .” (This phrase is the sufficient condition.)
  3. Abbreviate the sufficient condition: D
  4. Locate the necessary condition: “. . . are mammals.” (The phrase other than the sufficient condition is the necessary condition.)
  5. Abbreviate the necessary condition: M
  6. Combine the two conditions in the form of: sufficient → necessary

D → M

Every person who has gone to Yosemite remembers it.

Solution

  1. Locate the sufficient indicator: Every
  2. Locate the conditional phrase right after the sufficient indicator: “. . . person who has gone to Yosemite . . .” (This phrase is the sufficient condition.)
  3. Abbreviate the sufficient condition: GTY
  4. Locate the necessary condition: “. . . remembers it.” (The phrase other than the sufficient condition is the necessary condition.)
  5. Abbreviate the necessary condition: RI
  6. Combine the two conditions in the form of: sufficient → necessary

GTY → RI

Whenever I speak to my boss I get nervous.

Solution

  1. Locate the sufficient indicator: Whenever
  2. Locate the conditional phrase right after the sufficient indicator: “. . . I speak to my boss . . .” (This phrase is the sufficient condition.)
  3. Abbreviate the sufficient condition: STB
  4. Locate the necessary condition: “. . . I get nervous.” (The phrase other than the sufficient condition is the necessary condition.)
  5. Abbreviate the necessary condition: GN
  6. Combine the two conditions in the form of: sufficient → necessary

STB → GN

Every LSAT student wants to master formal logic.

Solution

  1. Locate the sufficient indicator: Every
  2. Locate the conditional phrase right after the sufficient indicator: “. . . LSAT student . . .” (This phrase is the sufficient condition.)
  3. Abbreviate the sufficient condition: LS
  4. Locate the necessary condition: “. . . wants to master formal logic.” (The phrase other than the sufficient condition is the necessary condition.)
  5. Abbreviate the necessary condition: WMFL
  6. Combine the two conditions in the form of: sufficient → necessary

LS → WMFL

1c. Sufficient: No / None

Meet the tilde: ~

That squiggly line (~) or a slash through symbolizes the opposite or an inversion. In this course, we use both the tilde and the slash because you’ll see both versions in LSAT courses. For no/none, we put the tilde on the necessary condition.

None of the canned jellybeans are purple.

Diagram of Quote

Solution:
1. Locate the sufficient indicator: None
2. Locate the conditional phrase right after the sufficient indicator: “. . . of the canned jellybeans . . .” (This phrase is the sufficient condition.)
3. Abbreviate the sufficient condition: CJ
4. Locate the necessary condition: “. . . are purple.” (The phrase other than the sufficient condition is the necessary condition.)
5. Abbreviate the necessary condition: P
6. Using the sufficient indicator “none” means putting a tilde (~) on the necessary condition for negation: ~(P) = ~P
7. Combine the two conditions in the form of: sufficient → necessary

CJs →  ~P

No human has stepped foot on Mars.

Diagram of Quote

Solution:
1. Locate the sufficient indicator: No
2. Locate the conditional phrase right after the sufficient indicator: “. . . human . . .” (This phrase is the sufficient condition.)
3. Abbreviate the sufficient condition: H
4. Locate the necessary condition: “. . . has stepped foot on Mars.” (The phrase other than the sufficient condition is the necessary condition.)
5. Abbreviate the necessary condition: SFM
6. Using the sufficient indicator “no” means putting a tilde (~) on the necessary condition for negation: ~(SFM) = ~SFM
7. Combine the two conditions in the form of: sufficient → necessary

H →  ~SFM

No Great White Sharks are vegetarians.

Diagram of Quote

Solution:
1. Locate the sufficient indicator: No
2. Locate the conditional phrase right after the sufficient indicator: “. . . Great White Sharks . . .” (This phrase is the sufficient condition.)
3. Abbreviate the sufficient condition: GWS
4. Locate the necessary condition: “. . . are vegetarians.” (The phrase other than the sufficient condition is the necessary condition.)
5. Abbreviate the sufficient condition: V
6. Using the sufficient indicator “none” means putting a tilde (~) on the necessary condition for negation: ~(V) = ~V
7. Combine the two conditions in the form of: sufficient → necessary

GWS →  ~V

1d. Sufficient: Never

You’ll typically use the ~ symbol in “never” statements on the necessary condition.

If you can’t beat them, join them.

Diagram of Quote

Solution:
1. Locate the sufficient indicator: If
2. Locate the conditional phrase right after the sufficient indicator: “. . . you can’t beat them . . .” (This phrase is the sufficient condition.)
3. Abbreviate the sufficient condition: ~B
4. Locate the necessary condition: “. . . join them.” (The phrase other than the sufficient condition is the necessary condition.)
5. Abbreviate the necessary condition: J
6. Combine the two conditions in the form of: sufficient → necessary

~B → J

If you can count your money, you don’t have a billion dollars.
-J. Paul Getty

Diagram of Quote

Solution:
1. Locate the sufficient indicator: If
2. Locate the conditional phrase right after the sufficient indicator: “. . . you can count your money . . .” (This phrase is the sufficient condition.)
3. Abbreviate the sufficient condition: CYM
4. Locate the necessary condition: “. . . you don’t have a billion dollars.” (The phrase other than the sufficient condition is the necessary condition.)
5. Abbreviate the necessary condition: ~B
6. Combine the two conditions in the form of: sufficient → necessary

CYM → ~B

2. NECESSARY CONDITIONS

Necessary Conditions Video Summary

  • 0:24 – The necessary condition is on the right side of a conditional statement (if-then relationship).
  • 1:38 – Note: Something to look out for in the LSAT is to avoid reversing the direction of conditional statements because they are not equivalent statements.
  • 1:50 – There are keywords that help you identify necessary conditions. These are called necessary indicators and they are listed on the LSAT Necessary Indicators sub-section.
  • 2:02 – For example: Only if Liam goes to the movie premiere will Lily go. The keywords “only if” tells us that the phrase “. . . Liam goes to the movie premiere . . .” is the necessary condition, so the phrase “. . . will Lily go.” is the sufficient condition.
  • 2:34 – Note: In cases where the words start with the same letter, you can use the whole words when diagramming to avoid confusion.
  • 3:04 – We can then diagram the conditional statement as follow: Lily → Liam.
  • 3:10 – Let us consider another example: A successful landing on Mars depends on entering the atmosphere at 14°. The necessary indicator “depends on” tells us that the phrase “. . . entering the atmosphere at 14°.” (14°) is the necessary condition, while the phrase “A successful landing on Mars . . .” (SL) is the sufficient condition. We can diagram this as: SL → 14°.
  • 3:50 – As another example, consider the statement: You don’t deserve praise for something unless you did it deliberately.
  • 3:56 – The keyword “unless” gives us the necessary condition “. . . you did it deliberately” (D), but it also requires us to apply a negation to the sufficient condition. It belongs to a set of unique keywords that functions similarly with others such as “until” and “except”. The sufficient condition then is “You don’t deserve praise for something . . .” (~P).
  • 4:44 – We can then diagram this as follows: ~(~P) → D which we can simplify as P →D.

LSAT Necessary Indicators
sufficient → [necessary indicator] necessary
Only
Only if
Only when
Relies on
Depends on
Must
Requires

See at 4:25 in the video:
~sufficient → [nec. indicator] necessary
(when you build this you have to put a tilde in front of the sufficient).
Unless
Until
Except

2a. Diagram Necessary Conditionals

To finish a marathon you must run 26 miles.

 [sufficient] → necessary indicator [necessary]

1. Locate the necessary indicator: To finish a marathon you must run 26 miles.

2. Locate the [necessary phrase] after the necessary indicator: must [run 26 miles]. (that phrase is the necessary conditionthe second part of the diagram).

3. Abbreviate it: R26 (run 26)

4. Locate the sufficient in the conditional:  …[To finish a marathon.] (that’s the sufficient conditionthe first part of the diagram).

5. Abbreviate it: FM (finish marathon)

6. Put abbreviations into a sufficientnecessary diagram: FMR26

Unless you run 26 miles, you can’t finish a marathon.

~[sufficient] → necessary indicator [necessary]

Note that unless, except, and until require a negation of the sufficient as explained in video above (4:26).

1. Locate the necessary indicator: Unless you run 26 miles…

2. Locate the [necessary phrase] after the necessary indicator: Unless [you run 26 miles]. (that phrase is the necessary conditionthe second part of the diagram).

3. Abbreviate it: R26 (run 26)

4. Locate the sufficient in the conditional:  …[you can’t finish a marathon.] (that’s the sufficient conditionthe first part of the diagram).

5. Abbreviate it: (~FM) (can’t finish marathon)

6. Since we are using unless, we put a tilde in front of the sufficient condition: ~(~FM) note: the double negatives cancel out.

7. Put abbreviations into a sufficientnecessary diagram: FM → R26

2b. Necessary: Only / Only If

Only indicates the necessary condition (the second item in the conditional).

Only coffee can get Ricky up in the morning.

Solution

  1. Locate the necessary indicator: Only
  2. Locate the conditional phrase which is right after the necessary indicator: “. . . coffee . . .” (This phrase is the necessary condition.)
  3. Abbreviate the necessary condition: C
  4. Locate the sufficient condition: “. . . get Ricky up in the morning.” (The phrase other than the necessary condition is the sufficient condition.)
  5. Abbreviate the sufficient condition: RUM
  6. Combine the two conditions in the form of: sufficient → necessary

RUM → C

Only dogs bark at vacuum cleaners. 

Solution

  1. Locate the necessary indicator: Only
  2. Locate the conditional phrase which is right after the necessary indicator: “. . . dogs . . .” (This phrase is the necessary condition.)
  3. Abbreviate the necessary condition: D
  4. Locate the sufficient condition: “. . . bark at vacuum cleaners.” (The phrase other than the necessary condition is the sufficient condition.)
  5. Abbreviate the sufficient condition: BVC
  6. Combine the two conditions in the form of: sufficient → necessary

BVC → D

It is only the ignorant who despise education.
-Publilius Syrus

Diagram of Quote

Solution:
1. Locate the necessary indicator: Only
2. Locate the conditional phrase right after the necessary indicator: “. . . the ignorant . . .” (This phrase is the necessary condition.)
3. Abbreviate the necessary condition: I
4. Locate the sufficient condition: “. . . who despise education.” (The phrase other than the necessary condition is the sufficient condition.)
5. Abbreviate the sufficient condition: DE
6. Combine the two conditions in the form of: sufficient → necessary

DE → I

The only truth is music.
-Jack Kerouac

Diagram of Quote

Solution:
1. Locate the necessary indicator: Only
2. Locate the conditional phrase right after the necessary indicator: “. . . truth . . .” (This phrase is the necessary condition.)
3. Abbreviate the necessary condition: T
4. Locate the sufficient condition: “. . . is music.” (The phrase other than the necessary condition is the sufficient condition.)
5. Abbreviate the sufficient condition: M
6. Combine the two conditions in the form of: sufficient → necessary

T → M

You can use the funds in my other bank account only in cases of emergency.

Solution

  1. Locate the necessary indicator: Only
  2. Locate the conditional phrase which is right after the necessary indicator: “. . . in cases of emergency.” (This phrase is the necessary condition.)
  3. Abbreviate the necessary condition: CE
  4. Locate the sufficient condition: “You can use the funds in my other bank account . . .” (The phrase other than the necessary condition is the sufficient condition.)
  5. Abbreviate the sufficient condition: UFBA
  6. Combine the two conditions in the form of: sufficient → necessary

UFBA → CE

Going to another country requires having a passport.

Solution

  1. Locate the necessary indicator: requires
  2. Locate the conditional phrase which is right after the necessary indicator: “. . . having a passport.” (This phrase is the necessary condition.)
  3. Abbreviate the necessary condition: HP
  4. Locate the sufficient condition: “Going to another country . . .” (The phrase other than the necessary condition is the sufficient condition.)
  5. Abbreviate the sufficient condition: GAC
  6. Combine the two conditions in the form of: sufficient → necessary

GAC → HP

The candidate who I will vote for depends on my political leanings.

Solution

  1. Locate the necessary indicator: depends on
  2. Locate the conditional phrase which is right after the necessary indicator: “. . . political leanings.” (This phrase is the necessary condition.)
  3. Abbreviate the necessary condition: PL
  4. Locate the sufficient condition: “The candidate who I will vote for . . .” (The phrase other than the necessary condition is the sufficient condition.)
  5. Abbreviate the sufficient condition: CIV
  6. Combine the two conditions in the form of: sufficient → necessary

CIV → PL

The company won’t reconnect their service unless you pay the overdue bill.

Solution

  1. Locate the necessary indicator: unless (You have to negate the sufficient condition when the necessary indicator “unless” is used.)
  2. Locate the conditional phrase which is right after the necessary indicator: “. . . you pay the overdue bill.” (This phrase is the necessary condition.)
  3. Abbreviate the necessary condition: POB
  4. Locate the sufficient condition: “The company won’t reconnect their service . . .” (The phrase other than the necessary condition is the sufficient condition.)
  5. Abbreviate the sufficient condition: ~CRS)
  6. Using the necessary indicator “unless” means putting a tilde (~) in the sufficient condition for negation: ~(~CRS) = CRS
  7. Combine the two conditions in the form of: sufficient → necessary

CRS → POB

I may be able to attend the party only if they announce the date and time asap.

Solution

  1. Locate the necessary indicator: only if
  2. Locate the conditional phrase which is right after the necessary indicator: “. . . they announce the date and time asap.” (This phrase is the necessary condition.)
  3. Abbreviate the necessary condition: ADT
  4. Locate the sufficient condition: “I may able to attend the party . . .” (The phrase other than the necessary condition is the sufficient condition.)
  5. Abbreviate the sufficient condition: AP
  6. Combine the two conditions in the form of: sufficient → necessary

AP → ADT

Every student taking a master’s degree has a bachelor’s degree.

Solution

  1. Locate the sufficient indicator: Every
  2. Locate the conditional phrase which is right after the sufficient indicator: “. . . student taking a master’s degree . . .” (This phrase is the sufficient condition.)
  3. Abbreviate the sufficient condition: TMD
  4. Locate the necessary condition: “. . . has a bachelor’s degree . . .” (The phrase other than the sufficient condition is the necessary condition.)
  5. Abbreviate the necessary condition: HBD
  6. Combine the two conditions in the form of: sufficient → necessary

TMD → HBD

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Next LSAT: October 28th