Mental Models Toolkit

Framework

IRON LAW: Use Multiple Models, Not Just Your Favorite

"To a man with a hammer, everything looks like a nail." (Munger)
A single mental model creates blind spots. Apply 2-3 models from
DIFFERENT disciplines to any important decision. Where models agree,
confidence is high. Where they disagree, the disagreement reveals
the most important dimension of the decision.

Core Mental Models (Cross-Disciplinary)

From Physics/Engineering

Model	Principle	Application
Inversion	Instead of "how do I succeed?", ask "how would I fail?" Then avoid that.	Risk management, pre-mortem
Second-order effects	Every action has consequences, which have consequences. Think two steps ahead.	Policy design, strategy
Entropy	Systems tend toward disorder without energy input. Things decay by default.	Maintenance, quality, relationships

From Biology

Model	Principle	Application
Evolution/natural selection	What survives is what's adapted, not what's "best" in absolute terms.	Market competition, product-market fit
Red Queen effect	You must keep improving just to stay in the same place (because competitors improve too).	Competitive strategy
Niche specialization	Generalists and specialists coexist because they serve different niches.	Market positioning, career strategy

From Mathematics/Statistics

Model	Principle	Application
Pareto principle (80/20)	~80% of effects come from ~20% of causes.	Prioritization, resource allocation
Regression to the mean	Extreme results tend to be followed by more average ones.	Performance evaluation, forecasting
Bayes' theorem	Update beliefs based on new evidence, weighted by prior probability.	Decision-making under uncertainty

From Psychology

Model	Principle	Application
Incentive-caused bias	People do what they're incentivized to do, not what you ask them to do.	Compensation design, policy design
Circle of competence	Know what you know and what you don't. Stay within your expertise for high-stakes decisions.	Self-awareness, delegation
Hanlon's razor	Never attribute to malice what is adequately explained by ignorance or incompetence.	Conflict resolution, workplace dynamics

Application Method

1. State the decision or problem
2. Select 2-3 relevant models from different disciplines
3. Apply each model to the situation — what does it suggest?
4. Compare conclusions — where do they agree? Where do they disagree?
5. Synthesize — the disagreement reveals the key trade-off to resolve

Output Format

# Multi-Model Analysis: {Decision}

## Models Applied
| Model | Discipline | Insight |
|-------|-----------|---------|
| {model 1} | {field} | {what this model says about the situation} |
| {model 2} | {field} | {what this model says} |
| {model 3} | {field} | {what this model says} |

## Convergence
{Where models agree — high confidence}

## Divergence
{Where models disagree — key trade-off to resolve}

## Synthesis
{Recommended decision based on multi-model analysis}

Gotchas

• Models are simplifications: Every model omits something. The map is not the territory. Use models as lenses, not as truth.
• Model inventory grows over time: Start with 10-15 core models. Add new ones as you encounter new domains. Quality of application matters more than quantity of models.
• Some models conflict by design: Inversion says "avoid failure." Evolution says "failure is how you learn." The conflict is resolved by context: avoid catastrophic failure, embrace recoverable failure.
• Don't force-fit: Not every model applies to every situation. If a model doesn't naturally illuminate the problem, skip it — don't stretch it to fit.

References

• For expanded mental models catalog (50+), see references/mental-models-catalog.md