Occam’s Razor and Hanlon’s Razor
Scope: The two “razors” in The Great Mental Models, Volume 1: Occam’s (prefer the explanation with the fewest moving parts) and Hanlon’s (do not attribute to malice what is more easily explained by stupidity), with the limits the authors set on each.
Occam’s Razor
“Simpler explanations are more likely to be true than complicated ones. This is the essence of Occam’s razor, a classic principle of logic and problem solving.” — Parrish and Beaubien, The Great Mental Models
Use: “Instead of wasting your time trying to disprove complex scenarios, you can make decisions more confidently by basing them on the explanation that has the fewest moving parts. The more complicated the explanation for something, the more skeptical you should be.” Why simple wins: “Simple explanations are easier to falsify, easier to understand, and generally more likely to be correct,” while “complexity takes work to unravel, manage, and understand.”
Limits the authors set:
- It is “not an iron law but a tendency and a mindset”: it applies “if all else is equal—that is, if two competing models both have equal explanatory power.”
- “Irreducible complexity, like simplicity, is a part of our reality. Therefore, we can’t use Occam’s razor to create artificial simplicity.” The code analogy: an explanation “can be simplified only to the extent that it can still provide an accurate understanding.”
- The safeguard against over-simplifying is Sagan’s “extraordinary claims require extraordinary proof.”
- “A theory that is too simple may fail to capture reality, and one that is too complex risks collapsing under its own weight.”
Hanlon’s Razor
“We should not attribute to malice that which is more easily explained by stupidity. In a complex world, using this model helps us avoid paranoia and ideology.”
The mechanism: “The explanation most likely to be right is the one that contains the least amount of intent.” Motives that need little energy (“ignorance or laziness”) are more likely than ones requiring “active malice.” The authors tie the error to vividness: “We’re deeply affected by vivid, available evidence, to such a degree that we’re willing to make judgments that violate simple logic,” and compare assuming intent to the Linda problem (bank teller and feminist).
Behavioral payoff: “When we assume stupidity rather than malice, we respond differently. Instead of getting defensive or lashing out, we approach the situation with empathy and clarity.” It reduces “unnecessary drama and stress” and points toward “practical solutions instead of descending into blame and recrimination.” It also keeps options open: “we look for options instead of missing opportunities.”
Limit: “This isn’t to say that genuine malice doesn’t exist. It does.” The razor is a prior, not a verdict; the guidance is to resist sinister motives “without overwhelming evidence.”
How the Two Fit Together
Both razors are priors that cut the cost of explanation
Each tells you which hypothesis to try first (fewest assumptions; least intent), not which is certain. Both are therefore probability statements in disguise, and both hold only “if all else is equal.” See Probabilistic Thinking and Fat Tails for updating when the evidence says otherwise.
- Against map-fixation: an over-complicated or conspiratorial explanation is often a map with too many invented features; see The Map Is Not the Territory.
- With second-order thinking: an uncharitable reaction to an error has its own downstream cost; see Second-Order Thinking on trust.
- With the structure view of trust: McKeown’s point that when trust fails “most people point at the other person” while the cause may be the relationship structure is Hanlon’s razor applied to teams: see High-Trust Structures.