| name | critical-thinking-logical-reasoning |
| description | Surface hidden assumptions, detect logical fallacies, examine evidence quality, and stress-test arguments before committing to them. |
| group | thinking |
| keywords | ["critical-thinking","logical-reasoning","fallacies","assumptions","evidence","argument","analysis","reasoning"] |
| task_strategies | ["spike","investigation"] |
| stream_affinity | ["roadmap","research"] |
| allowed-tools | ["Read","Glob","Grep","AskUserQuestion"] |
| status | experimental |
| source | Richard Paul & Linda Elder — Critical Thinking (2006); Kahneman — Thinking Fast and Slow (2011); Aristotle — Prior Analytics |
| acquired | 2026-06-15 |
Critical Thinking & Logical Reasoning
Find what's wrong with the argument before you commit to it.
Critical thinking is not skepticism for its own sake — it's the discipline of examining the quality of reasoning before acting on it. The goal is to catch flawed logic, hidden assumptions, and weak evidence before they become expensive decisions.
When to use
- Evaluating a proposal, plan, or recommendation
- When an argument sounds compelling but feels off
- Before accepting data-driven claims
- When debugging a persistent wrong belief in a team
- After research — to evaluate what you found before applying it
- Pairs with
/brana:challenge for adversarial review; /brana:first-principles for rebuilding from what's actually true
Step 1 — Identify the claim
What is being asserted?
AskUserQuestion: "What claim, argument, or reasoning are we examining?"
State it in the clearest possible form. Often the act of stating a claim precisely already reveals its weakness.
Step 2 — Surface hidden assumptions
Every argument rests on assumptions. List them all:
Existential assumptions — "X exists" or "X is real"
- Example: "Our users are power users" assumes that power users are a significant segment
Causal assumptions — "X causes Y"
- Example: "More features = more retention" assumes features are the bottleneck for retention
Comparative assumptions — "X is better than Y"
- Example: "Rewriting will be faster" assumes the rewrite won't hit the same problems
Scoping assumptions — "This applies to all of / most of / some of X"
- Example: "Users want this" means... how many? Which users?
For each assumption:
- Is it stated or hidden?
- What evidence supports it?
- What would change if it's wrong?
Step 3 — Examine evidence quality
For each claim, ask:
| Question | What to look for |
|---|
| Source | Primary source or hearsay? Who funded the research? |
| Sample | How big? How representative? Self-selected? |
| Method | Controlled? Correlation confused for causation? |
| Recency | Is this still true? Context may have changed |
| Completeness | What evidence AGAINST the claim exists? |
Evidence strength scale:
- Strong: large controlled study, multiple independent replications
- Moderate: single study, observational data, expert consensus
- Weak: anecdote, single data point, self-report, authority claim
- None: assertion without evidence
Step 4 — Check for logical fallacies
Common fallacies in technical and business reasoning:
| Fallacy | Pattern | Example |
|---|
| Ad hominem | Attack the person, not the argument | "Of course they'd say that, they're from [company]" |
| Appeal to authority | Authority = truth | "Google does it this way" |
| False dichotomy | Only two options | "We either rewrite or stay stuck forever" |
| Slippery slope | One step inevitably leads to extreme | "If we add this exception, everything will become exceptions" |
| Strawman | Misrepresent the opposing view | "So you're saying we should never refactor?" |
| Correlation/causation | A happens with B, therefore A causes B | "Users who use feature X retain better, so feature X causes retention" |
| Sunk cost | Past investment justifies future investment | "We've already spent 3 months on this" |
| Availability heuristic | Recent/memorable = common | "I've seen this bug before so it must be frequent" |
| Confirmation bias | Seeking evidence that confirms, ignoring disconfirming | Only citing studies that support the conclusion |
| Base rate neglect | Ignoring prior probability | "Our competitor failed at this but we're better" |
Mark each fallacy found: [claim] → [fallacy type] → [why it's wrong here]
Step 5 — Evaluate the argument structure
Is the reasoning valid? (Does the conclusion follow from the premises?)
Is the reasoning sound? (Are the premises true AND does the conclusion follow?)
Premise 1: [X]
Premise 2: [Y]
∴ Conclusion: [Z]
Valid? [yes/no] — does Z follow from X and Y?
Sound? [yes/no] — are X and Y actually true?
An argument can be valid (correct structure) but unsound (false premises). Most flawed reasoning is unsound, not invalid.
Step 6 — Output
**Critical thinking analysis of [claim/argument]**
Core claim: [restated precisely]
Hidden assumptions found: [N]
Critical: [most load-bearing assumption]
Status: [supported/unsupported/false]
Evidence quality: [strong/moderate/weak/none]
Key gap: [what evidence is missing]
Fallacies detected: [list]
Argument structure: [valid/invalid] + [sound/unsound]
Verdict:
Accept as is / Accept with caveats / Reject / Needs more evidence
Key condition: [what would change the verdict]
Notes
- The goal is not to win arguments — it's to make better decisions by reasoning better
- Steel-man before attacking: state the strongest version of the opposing argument first
- Kahneman's System 1/System 2: most reasoning errors come from System 1 (fast, intuitive) presenting conclusions to System 2 (slow, analytical) without flagging they're conclusions
- "I believe X" is not the same as "there is evidence for X" — distinguish confidence from evidence
- Strong critical thinking produces "I was wrong" as often as "they're wrong"
- Pair with
/brana:brainstorm after debunking — critique clears the space; brainstorm fills it
