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
- State the decision or problem
- Select 2-3 relevant models from different disciplines
- Apply each model to the situation — what does it suggest?
- Compare conclusions — where do they agree? Where do they disagree?
- 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