1. Occam’s Razor: explanations should never multiply causes without necessity; when multiple explanations are offered, the simplest, full explanation is preferable (via WikipediaSuper ThinkingThe Great Mental Models Volume 1The Skeptics’ Guide to the Universe)

2. Hanlon’s Razor: never attribute to malice that which is more easily explained by stupidity, carelessness, or laziness (via Wikipedia,Super ThinkingThe Great Mental Models Volume 1)

3. Hitchens’ Razor: what can be asserted without evidence can also be dismissed without evidence (via Wikipedia)

4. Alder’s Razor (or Newton’s Flaming Laser Sword): what cannot be settled by experiment is not worth debating (via Wikipedia)

5. Hume’s Guillotine: what ought to be cannot be deduced from what is (via Wikipedia)

6. Grice’s Razor (aka Principle of Charity, Giume’s razor): most people are bad at expressing themselves, so don’t interpret their words literally but rather by what they are most likely to mean (via Wikipedia)

7. Einstein’s Razor: make things as simple as possible, but no simpler (via Wikipedia)

8. Feynman’s Razor: if you can’t explain something to a child, you don’t understand it yourself; it’s only when you fully grasp a topic that you can distill it down to its essence (via Gurwinder Bhogal)

9. Gell-Mann’s Razor: assume every media article contains a percentage of false information (via George Mack, also see Gell-Mann amnesia effect)

10. Popper’s Razor: for a theory to be considered scientific, it must be falsifiable (via Wikipedia)

11. Russell’s Teapot: the philosophic burden of proof lies upon a person making empirically unfalsifiable claims, rather than shifting the burden of disproof to others (via Wikipedia)

12. Sagan’s Standard: extraordinary claims require extraordinary evidence (via Wikipedia)

13. Naval’s Razor: if you can’t decide between two choices, take the path that’s more difficult/painful in the short term; doing this will counteract hyperbolic discounting, the brain’s tendency to overestimate short term pain and underestimate long term pain (via Gurwinder Bhogal)

14. Discomfort Razor: the more uncomfortable the activity, the more likely it will lead to growth; the more comfortable the activity, the more likely it will lead to stagnation (via George Mack)

15. Tarzwell’s Razor: the more emotional you feel, the less you should trust your judgment (via Gurwinder Bhogal)

16. Bragging Razor: if someone brags about their success or happiness, assume it’s half what they claim; if someone downplays their success or happiness, assume it’s double what they claim (via George Mack)

17. Narcissism Razor: if worried about people’s opinions, remember they are too busy worrying about other people’s opinions of them (99% of the time you’re an extra in someone else’s movie) (via George Mack)

18. Charisma Razor: if a high-achieving person is charismatic, start with a level of skepticism for each idea they present; if a high-achieving person isn’t charismatic, start with a level of openness for each idea they present (via George Mack)

19.Luck Razor: if stuck with two equal options, pick the one that feels like it will produce the most luck later down the line (via George Mack)

20. Everyday Razor: if you go from doing a task weekly to daily, you achieve 7 years of output in 1 year; if you apply a 1% compound interest each time, you achieve 54 years of output in 1 year (via George Mack)

21. Network Razor: if you have two quality people that would benefit from an intro to one another, always do it (via George Mack)

22. Smart Friends Razor: if unsure about a small bet but your smart friends are sure, take the bet; if you wait for the rest of society to confirm it, you’ll be too late (via George Mack)

23. Early-Late Razor: if it’s a talking point on Reddit or Twitter, you might be early; if it’s a talking point on LinkedIn or Facebook, you’re definitely late (via George Mack)

24. Instagram Razor: when you see a photo of an influencer looking attractive on Instagram, assume there are 99 worse variations of that photo you haven’t seen and they just picked the best one (via George Mack)

25. 25+ Razor: if you’re 25+, assume your reactions about new technologies and trends are wrong; if someone under the age of 25 is obsessed with something new, don’t dismiss it until you’ve done 10+ hours on it (via George Mack)

Bonus — Elon’s Razor: the most entertaining outcome is the most likely (Elon’s variant on Occam’s Razor). Elon has described it over the years in various ways:

  • “The most entertaining outcome is the most likely (as seen from an external observer, not the participants).”
  • “The most entertaining outcome is the most likely (as seen by an unaffected third party).”
  • “The most entertaining outcome (as if we were in a movie) is the most likely.”
  • “The most entertaining outcome is the most likely – more interesting to the simulators.”
  • “It does often seem that the most entertaining belief or outcome is the most likely to prevail.”