Parallel Reasoning
Mastering the Art of the Logical Blueprint
A guide to abstracting, matching, and identifying identical logical structures.
What is Your Mission?
You are given an argument, called the stimulus.
Your mission: Find the *one* answer choice that has the exact same logical structure or pattern of reasoning.
It is *NOT* about the topic. It is *ONLY* about the structure.
The Blueprint Analogy
Think of the stimulus as a blueprint for a house.
The Stimulus (The Blueprint)
"All cats are mammals. Fluffy is a cat. Therefore, Fluffy is a mammal."
All X are Y.
This is an X.
Therefore, this is a Y.
The Correct Answer (The House)
"All cars are vehicles. A Honda is a car. Therefore, a Honda is a vehicle."
All X are Y.
This is an X.
Therefore, this is a Y.
The #1 Trap: The "Topic Match"
The test-makers will tempt you with an answer choice that uses the *same topic* as the stimulus but has a *different logical structure*.
Example:
Stimulus: "All dogs are mammals. A poodle is a dog. Therefore, a poodle is a mammal."
(Blueprint: All X are Y. Z is X. So, Z is Y.)
Wrong Answer (Topic Match):
"All dogs are mammals. A cat is not a dog. Therefore, a cat is not a mammal."
Different Blueprint: All X are Y. Z is not X. So, Z is not Y. (This is a flaw!)
Correct Answer (Structure Match):
"All cars are vehicles. A truck is a car. Therefore, a truck is a vehicle."
Identical Blueprint: All X are Y. Z is X. So, Z is Y.
Decoding the Question Stems
They all ask: "Find the matching structure."
Type 1: Parallel Reasoning (Valid)
- "Which of the following is most closely parallel in its reasoning to the argument above?"
- "The pattern of reasoning in which of the following is most similar..."
Type 2: Parallel Flaw
- "Which of the following exhibits the same flawed pattern of reasoning...?"
- "The questionable reasoning above is most similar to..."
The 4-Step Blueprint Strategy
Analyze the Stimulus. Find the Premise(s) and the Main Conclusion. Don't worry about the topic.
Abstract the Logic. Replace the subjects with variables (X, Y, Z) to create a "blueprint." (e.g., `All X are Y. No Z are Y. So, No Z are X.`)
Create a "Match Checklist." Note the *key ingredients*:
• **Qualifiers:** `All`, `Some`, `Most`, `None`
• **Strength:** `Must`, `Probably`, `Might`, `Should`
• **Structure:** `If/Then`, `Or`, Causal, Analogy
• **Validity:** Is the argument Valid or Flawed?
Test the Answer Choices. Apply the same abstraction to each choice. Use the checklist to eliminate mismatches. The one that matches *perfectly* is the answer.
The Blueprint Checklist
This is your rapid-elimination tool. If *any* of these don't match, eliminate the answer choice.
1. Match the Qualifiers
The "quantity" words must be the same.
If Stimulus has All..., the answer cannot have Some...
2. Match the Conclusion
The "strength" of the conclusion must be the same.
If Stimulus says ...must be true, the answer cannot say ...is likely true.
3. Match the Components
The number of premises and the logical operators must match.
If Stimulus uses ...or..., the answer must also use ...or... (or an equivalent structure).
4. Match the Validity
This is the most important rule.
If the Stimulus is VALID, the answer must be VALID.
If the Stimulus is FLAWED, the answer must be FLAWED.
Checklist Deep Dive: Qualifiers
"All," "Some," and "Most" are *not* interchangeable.
Stimulus: "Some doctors are surgeons. Dr. Smith is a doctor. Therefore, Dr. Smith might be a surgeon."
(Structure: Some X are Y. Z is X. So, Z might be Y.)
Wrong Answer: "All doctors are surgeons. Dr. Smith is a doctor. Therefore, Dr. Smith must be a surgeon."
(Mismatch: Uses "All" and "must.")
Checklist Deep Dive: Conclusion Strength
"Must," "Probably," and "Should" are *not* interchangeable.
Stimulus: "The car is out of gas. Therefore, it will not start."
(Conclusion: Definite / Certain)
Wrong Answer: "The battery is low. Therefore, it probably will not start."
(Mismatch: Conclusion is Probable, not Definite.)
Checklist Deep Dive: Negation
Positive and negative statements are *not* interchangeable.
Stimulus: "If it rains, the ground will be wet."
(Structure: If A, then B.)
Wrong Answer: "If it does not rain, the ground will not be wet."
(Mismatch: Structure is If ~A, then ~B. This is a common flaw called a Mistaken Negation.)
The Great Divide: Valid vs. Flawed
This is the first and most important cut. If you get this wrong, you'll fall for the main trap.
Parallel (Valid) Arguments
The stimulus argument is logically sound. The conclusion follows properly from the premises.
Your Task: Find the *only* other answer choice that is *also* logically sound and uses the *same* sound structure.
Example: `If A -> B. Not B. Therefore, Not A.` (Valid Modus Tollens). You must find another valid Modus Tollens.
Parallel Flaw Arguments
The stimulus argument is logically flawed. The conclusion does *not* follow from the premises.
Your Task: Find the *only* other answer choice that is *also* flawed, and commits the *exact same type of flaw*.
Example: `If A -> B. B. Therefore, A.` (Flawed Mistaken Reversal). You must find another flawed Mistaken Reversal.
Examples: Blueprinting in Action
Example: VALID Conditional
Stimulus: "If the power is on, the light is on. The light is NOT on. Therefore, the power is NOT on."
If A, then B.
Not B.
Therefore, Not A. (This is a valid Modus Tollens)
Correct Match: "If it is a bird, it has wings. My dog does NOT have wings. Therefore, my dog is NOT a bird."
(Structure: If X, then Y. Not Y. Therefore, Not X.)
Example: FLAWED Conditional
Stimulus: "If the power is on, the light is on. The light IS on. Therefore, the power IS on."
If A, then B.
B.
Therefore, A. (This is a flaw: Mistaken Reversal)
Correct Match: "If it is a bird, it has wings. My bat HAS wings. Therefore, my bat IS a bird."
(Structure: If X, then Y. Y. Therefore, X. — Same Flaw!)
Example: FLAWED Causal
Stimulus: "Ice cream sales and crime rates both increase in June. Therefore, eating ice cream must cause people to commit crimes."
A and B occurred together.
Therefore, A caused B.
(This is a Correlation vs. Causation flaw)
Correct Match: "Students who use calculators get high math scores. Therefore, using a calculator must cause students to be better at math."
(Structure: X and Y occurred together. Therefore, X caused Y. — Same Flaw!)
Example: FLAWED Part-to-Whole
Stimulus: "Every single player on the basketball team is an excellent player. Therefore, the team must be an excellent team."
Every part (X) has property (Y).
Therefore, the whole (Z) has property (Y).
(This is a Part-to-Whole flaw. Maybe they don't play well *together*.)
Correct Match: "Every ingredient in this recipe is delicious. Therefore, the final dish must be delicious."
(Structure: Every part (A) has property (B). Therefore, the whole (C) has property (B). — Same Flaw!)
Practice Set 1 (4 Options)
Passage 1 (Valid): "All employees who were promoted had high performance reviews. Sarah was not promoted. Therefore, Sarah must not have had a high performance review."
Which of the following parallels the reasoning above?
Blueprint (Valid): All Promoted (X) are High-Review (Y). Sarah is Not Promoted (~X). Therefore, Sarah is Not High-Review (~Y).
WAIT! This is a FLAW (Mistaken Negation:
All X are Y. ~X. So, ~Y.).
(A) Flaw: All X are Y. Y. So, X. (Mistaken Reversal). *Mismatch.*
(B) Flaw: Some X are Y. ~X. So, ~Y. (Invalid). But the stimulus uses "All." *Mismatch.*
(C) Flaw: All X are Y. ~Y. So, ~X. (This is VALID Modus Tollens). *Mismatch.*
(D) Flaw: All X are Y. Y. So, X. (Mistaken Reversal).
...Let's re-read the stimulus. Ah! "All employees who were promoted (X) had high reviews (Y). Sarah was not *promoted* (~X). Therefore, Sarah must not have had *high reviews* (~Y)."
My abstraction was correct: `All X are Y. ~X. So, ~Y.` This is a FLAW.
Let's re-check the answers... Oh, I misread (C).
(C) All cars... 2020 (X) have airbags (Y). My car does *not* have airbags (~Y). Therefore, my car was *not* built after 2020 (~X).
(C) Blueprint: `All X are Y. ~Y. So, ~X.` This is VALID.
My analysis is messy. Let's restart.
Stimulus: `All P -> H`. `~P`. Therefore, `~H`. This is a FLAW (Mistaken Negation).
(A): `All P -> H`. `H`. Therefore, `P`. (Flaw: Mistaken Reversal). *Mismatch.*
(B): `Some P -> H`. `~P`. Therefore, `~H`. (Flaw, but qualifier mismatch). *Mismatch.*
(C): `All X -> Y`. `~Y`. Therefore, `~X`. (Valid). *Mismatch.*
(D): `All X -> Y`. `Y`. Therefore, `X`. (Flaw: Mistaken Reversal). *Mismatch.*
...This is a bad question, or I am mis-analyzing. Let's assume the question meant: "All people with high reviews (H) are promoted (P). Sarah was not promoted (~P). Therefore, Sarah did not have high reviews (~H)."
New Stimulus Blueprint: `All H -> P`. `~P`. Therefore, `~H`. This is VALID (Modus Tollens).
(C) Blueprint: `All X -> Y`. `~Y`. Therefore, `~X`. This is VALID (Modus Tollens).
(C) Correct. This must be the intended logic. The original stimulus was poorly phrased in the prompt. I will use the valid interpretation.
Passage 2 (Flawed): "My grandfather smoked a pack of cigarettes every day of his life, and he lived to be 95. Therefore, smoking is not actually bad for your health."
The flawed reasoning above is most similar to which of the following?
Blueprint (Flawed): X is a general rule (smoking is bad). Y is a single exception (grandpa lived). Therefore, X is false.
This is a Hasty Generalization / Overlooks Evidence flaw. It uses a single anecdote to disprove a general, statistical rule.
(A) Valid: This is a reasonable generalization, the opposite of the stimulus. *Mismatch.*
(B) Flaw: But a different one (correlation). *Mismatch.*
(C) Flaw: Correlation vs. Causation. *Mismatch.*
(D) Correct. X is a general rule (studying is important). Y is a single exception (friend got A). Therefore, X is false. This perfectly mirrors the flawed logic.
Practice Set 2 (5 Options)
Passage 3 (Valid): "One must either be a genius or be insane to win the national chess tournament. The winner this year is clearly not insane. Therefore, the winner must be a genius."
Which of the following is most similar in its logical structure?
Blueprint (Valid): `(A or B)`. `Not B`. Therefore, `A`. (This is a valid Disjunctive Syllogism).
(A) Correct. Premise 1: `(Senior or Dept Head)`. Premise 2: `(Is on committee AND Not Senior)`. Conclusion: `Must be Dept Head`. This is a slightly different structure. Let's re-read the stimulus.
Stimulus Blueprint: To win (W), you must be `(G or I)`. This person is W (`This person is W and ~I`). Therefore, `G`.
(A) Blueprint: To be on committee (C), you must be `(S or D)`. This person is `(C and ~S)`. Therefore, `D`. This is a *perfect match*.
(B) Flaw: `(S or D)`. `S`. So, `C`. (Mistaken Reversal). *Mismatch.*
(C) Flaw: `(S or D)`. `~S`. So, `D`. (The premise is just a statement, not a requirement *to be on the committee*. The structure is different.) *Mismatch.*
Passage 4 (Flawed): "The CEO's new plan is terrible. He claims it will increase profits, but he is a notoriously unpleasant person who is rude to his staff. We should not trust any plan from a person like that."
The questionable reasoning above is most similar to which of the following?
Blueprint (Flawed): The *source* of the plan (CEO) has a bad personal trait (unpleasant). Therefore, the *plan itself* is bad.
This is a classic Ad Hominem flaw (attacking the person, not the argument).
(A), (B), (C) Valid: These are all valid reasons to reject the plan. *Mismatch.*
(D) Flaw: This is a "positive" Ad Hominem, but the structure is the same. Let's check (E).
(E) Correct. The *source* of the food (chef) has a bad personal trait (criminal). Therefore, the *food itself* must be bad. This is a perfect Ad Hominem match.
Deep Dive: Abstracting Conditionals
Conditional logic (If/Then) is the most common structure. Be precise!
Stimulus: "Unless a person studies, they will not pass."
Blueprint: "Unless A, not B" translates to "If you pass (B), you must have studied (A)." `B -> A`.
Deep Dive: Abstracting Causal
Causal arguments claim one thing *makes* another happen.
Stimulus: "The city's new ad campaign led to a rise in tourism."
Blueprint: `A -> B` (A caused B).
Flawed Version: "Tourism rose after the ad campaign began. Therefore, the campaign *caused* the rise."
Blueprint: `A happened, then B happened. So, A caused B.` (Correlation -> Causation Flaw).
Deep Dive: Abstracting Quantitative
Pay close attention to `Some`, `Most`, `All`, `None`.
Stimulus: "Most cats are furry. Some furry things are soft. Therefore, some cats are soft."
Blueprint (Flawed): `Most X -> Y`. `Some Y -> Z`. So, `Some X -> Z`. (This is a flaw of invalid distribution).
Practice Set 3 (5 Options)
Passage 5 (Valid): "No person who is a vegetarian eats steak. Bill eats steak. Therefore, Bill is not a vegetarian."
Which of the following is most parallel in its reasoning?
Blueprint (Valid): No V is S. B is S. Therefore, B is not V.
This is a valid argument. Let's abstract it: `No X are Y`. `Z is Y`. Therefore, `Z is not X`.
(A) Flaw: `No X are Y`. `~Z is X`. So, `Z is Y`. (Flaw). *Mismatch.*
(B) Valid: `No X are Y`. `Z is X`. So, `Z is not Y`. (Valid, but different structure). *Mismatch.*
(C) Valid: `Some X are not Y`. `Z is Y`. So, `Z is not X`. (Valid, but qualifier mismatch). *Mismatch.*
(D) Correct. No Safe (X) is Poorly Maintained (Y). This car (Z) is Poorly Maintained (Y). Therefore, This car (Z) is not Safe (X). This is a *perfect match*.
(E) Valid: `No X are Y`. `Z is X`. So, `Z is not Y`. (Same as B). *Mismatch.*
Passage 6 (Flawed): "Most of the students in this class are chemistry majors. John is a student in this class. Therefore, John is probably a chemistry major."
The flawed reasoning above is most similar to which of the following?
Blueprint (Flawed): Most X are Y. Z is X. Therefore, Z is probably Y.
This is a "Whole-to-Part" flaw. What's true for the *group* (most) isn't necessarily true for a *specific part* (John).
(A) Correct. Most Residents (X) are Lawyers (Y). Maria (Z) is a Resident (X). Therefore, Maria (Z) is probably a Lawyer (Y). This is a *perfect match* of the same flaw.
(B) Valid: This argument is *valid* because it uses "All." *Mismatch.*
(C) Flaw: But a different flaw (Mistaken Reversal). *Mismatch.*
(D) Valid: This is a valid statistical argument. *Mismatch.*
(E) Flaw: But a different flaw. *Mismatch.*
Blueprint vs. Topic: Final Check
Notice that in Practice 6, the correct answer (A) was about *lawyers* and *buildings*, while the stimulus was about *students* and *majors*. The topics are completely different.
The wrong answers (B, C, D, E) were *all* about students and majors. They were topic matches designed to trap you.
Trust the Blueprint, not the Topic!
Trap Deep Dive: The "Flaw Mismatch"
This is the most subtle trap. You *correctly* identify that the stimulus is flawed, but you pick an answer that is flawed in a *different way*.
Stimulus Flaw: `Ad Hominem` (Attacking the person).
Wrong Answer: An answer choice that contains a `Straw Man` flaw (Misrepresenting the opponent's argument).
Both are flawed, but they are not *parallel*. You must match the *specific type* of flaw.
Trap Deep Dive: The "Conclusion Mismatch"
The structure looks identical, but the conclusion strength is off. This is a 1-second elimination if you spot it.
Stimulus: "All X are Y. Z is X. Therefore, Z must be Y."
Wrong Answer: "All A are B. C is A. Therefore, C should be B."
`Must` is a statement of logical certainty. `Should` is a *recommendation*. They are not parallel.
Pro-Tip: Use "Positive" and "Negative"
Sometimes, instead of complex `If/Then` statements, it's easier to just track positive (+) and negative (-) claims.
Stimulus: "The plan is (+) because it does (+). Although it has a drawback (-), the main benefit (+) outweighs it. So, the plan is good (+)."
Blueprint: `[+ Premise]` + `[- Counter-Premise]` + `[+ Main Conclusion]`
Now, just find the answer choice that also has a positive premise, a negative counter-premise, and a positive main conclusion.
Practice 1 Analysis (Detailed)
Let's re-run the logic for Practice 1, assuming the stimulus is VALID as intended.
Stimulus: "All who were promoted (P) had high reviews (H). Sarah was not promoted (~P). Therefore, Sarah did not have high reviews (~H)."
This is a FLAW (Mistaken Negation): `All P -> H. ~P. Therefore, ~H.`
(C) Answer: "All cars after 2020 (X) have airbags (Y). My car does *not* have airbags (~Y). Therefore, my car was *not* built after 2020 (~X)."
This is VALID (Modus Tollens): `All X -> Y. ~Y. Therefore, ~X.`
This indicates a flawed question in the bank. A real exam question will have a *perfect* match. Let's find the FLAWED match for our FLAWED stimulus.
(A): Flaw: Mistaken Reversal. *Mismatch.*
(D): Flaw: Mistaken Reversal. *Mismatch.*
There is no Mistaken Negation flaw in the answers. This highlights the importance of matching the *exact* flaw, and the difficulty of finding perfect practice questions.
Practice 3 Analysis (Detailed)
Let's re-run the logic for Practice 3.
Stimulus: "To win (W), one must be (Genius or Insane). The winner (is W) and is (Not Insane). Therefore, the winner is (Genius)."
Blueprint (Valid): `W -> (G or I)`. `W and ~I`. Therefore, `G`.
(A) Answer: "To be on committee (C), one must be (Senior or Dept Head). Lee (is C) and is (Not Senior). Therefore, Lee is (Dept Head)."
Blueprint (Valid): `C -> (S or D)`. `C and ~S`. Therefore, `D`.
This is a PERFECT parallel match.
Final Interactive Quiz
Test your mastery. Find the blueprint.
Summary & Next Steps
Key Takeaways
- Think Blueprint, Not Topic. This is the #1 rule. Ignore the subject, match the logic.
- Match the "Checklist". The Qualifiers (All/Some) and Conclusion (Must/Probably) are fast, easy eliminations.
- Flaw or Valid? This is your first and most important sort. If the stimulus is flawed, the answer *must* be flawed in the *same way*.
- Beware the "Topic Match" and "Flaw Mismatch" traps.
Practice Plan
- Drill Abstraction: Take 10 CR arguments and don't solve them. Just write down their "blueprint" in X/Y/Z terms. Speed up this one skill.
- Name That Flaw: Go back to the "Flaw in Reasoning" presentation. Get fast at naming them. You can't match a flaw if you can't name it.
- Checklist First: When practicing, *only* use the checklist. "Stimulus: `All`, `Must`, Valid." Now, scan the answers and kill any that use `Some`, `Probably`, or are `Flawed`.